Roasted Veggie Casserole is one of those recipes I make when I open my fridge and see a rainbow of vegetables staring back at me. It’s basically taking whatever veggies you’ve got, roasting them until they’re caramelized and sweet, then drowning them in cheese sauce.
Love More Recipes? Try My Sheet Pan Garlic Butter Chicken and Veggies or this Chicken Caesar Wrap next.
Why You’ll Love This Recipe
Colorful, hearty, and full of flavor, this Roasted Veggie Casserole is a wholesome dish that celebrates seasonal vegetables. Roasted to perfection with olive oil and herbs, the veggies are then baked with a touch of cheese for extra richness. Perfect as a side or a light main, it’s a cozy and nutritious crowd-pleaser.
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Roasted Veggie Casserole: A Colorful, Cheesy Comfort Dish
- Total Time: 45-60 minutes
- Yield: 1 casserole
Description
A wholesome and delicious roasted veggie casserole featuring caramelized vegetables coated in your choice of vegan or Mediterranean-style cheese sauce. This colorful, nutritious dish works as both a satisfying main course and hearty side dish. Packed with sweet potatoes, carrots, zucchini, broccoli, bell peppers, mushrooms, and cherry tomatoes, it’s perfect for meal prep and easily customizable with whatever vegetables you have on hand.
Ingredients
For the Roasted Vegetables:
- 4 cloves garlic, chopped
- 1 onion, sliced
- 1 large sweet potato, sliced
- 2 carrots, sliced
- 1 zucchini, sliced
- ½ head broccoli, broken into florets
- 1 red bell pepper, seeds and top removed and sliced
- 2 cups mushrooms (white preferred)
- 2 tablespoons olive oil
- 1 cup cherry tomatoes
- Seasonings as desired (I like garlic powder, Italian herbs, salt, and pepper)
For Vegan Cheese Sauce:
- ½ cup vegan cheese
- 1 cup nut or oat milk
- 2 tablespoons nutritional yeast
- 1 teaspoon paprika
- 2 tablespoons olive oil
- Seasonings to taste
For Mediterranean Diet Friendly Cheese Sauce:
- 1 tablespoon plus 2 teaspoons flour
- 1½ cups milk (use low to no fat milk or nut milk)
- ⅔ cup grated cheddar cheese
- Seasonings as desired
Instructions
Turn your oven to 450°F. Line a baking sheet with parchment or spray it. High heat is important here – that’s what makes the vegetables brown instead of just cooking.
Put all the vegetables except the cherry tomatoes in a bowl. Pour olive oil over them and add your seasonings. I use garlic powder, Italian seasoning, salt, and pepper but you can use whatever. Mix it with your hands.
Cut things about the same size. Doesn’t have to be perfect but if your sweet potato is in huge chunks and your zucchini is tiny pieces, they won’t cook at the same speed.
Spread everything on the baking sheet. Don’t pile them up. They need space or they’ll steam. Put them in the oven for 25-30 minutes. Stir them every 10 minutes.
They’re done when they’re soft and have brown edges. Those brown bits are where the flavor is.
Make your sauce while the vegetables roast.
Vegan: Put all the ingredients in a pot and stir constantly over medium heat. Don’t leave it or it’ll burn on the bottom. Takes 5-7 minutes to get thick. It should coat your spoon.
Regular: Whisk the flour, milk, and cheese in a pot over medium-low heat. Keep whisking. Don’t stop. Takes 8-10 minutes. Add salt and pepper when it’s thick.
Turn your oven to 350°F. Spray your casserole dish. Put the roasted vegetables in, add the cherry tomatoes, pour the cheese sauce over everything.
Bake for 5-10 minutes. This warms up the tomatoes and lets everything come together. Stir it before you serve so the sauce gets mixed in.
Notes
- Don’t overcrowd the baking sheet – if your veggies are piled up, they’ll steam instead of roast. Use two sheets if needed!
- Make sure your oven is fully preheated before adding vegetables. That initial blast of heat is crucial for caramelization.
- For the vegan sauce, if it gets too thick, thin it out with a splash more milk. Too thin? Let it simmer a bit longer.
- For the Mediterranean sauce, using room temperature cheese helps it melt more smoothly into the sauce.
- Common mistake: Adding the cherry tomatoes too early. They’ll turn to mush! Add them only at the assembly stage.
- Smart shortcut: Use pre-cut vegetables from the grocery store if you’re short on time. No judgment here!
- Prep Time: 15-20 minutes
- Cook Time: 30-40 minutes
- Category: Main Dish / Side Dish
- Method: Roasting
- Cuisine: American
Ingredient List
For the Roasted Vegetables:
- 4 cloves garlic, chopped
- 1 onion, sliced
- 1 large sweet potato, sliced
- 2 carrots, sliced
- 1 zucchini, sliced
- ½ head broccoli, broken into florets
- 1 red bell pepper, seeds and top removed and sliced
- 2 cups mushrooms (white preferred)
- 2 tablespoons olive oil
- 1 cup cherry tomatoes
- Seasonings as desired (I use garlic powder, Italian herbs, salt, pepper)
For Vegan Cheese Sauce:
- ½ cup vegan cheese
- 1 cup nut or oat milk
- 2 tablespoons nutritional yeast
- 1 teaspoon paprika
- 2 tablespoons olive oil
- Seasonings to taste
For Mediterranean Diet Friendly Cheese Sauce:
- 1 tablespoon plus 2 teaspoons flour
- 1½ cups milk (use low to no fat milk or nut milk)
- ⅔ cup grated cheddar cheese
- Seasonings as desired
Substitution Notes: Use whatever vegetables you have. I’ve done this with cauliflower, butternut squash, asparagus, Brussels sprouts. Just keep the total amount about the same so it fits on the pan. Any milk works – dairy, oat, almond, whatever’s in your fridge.
Why These Ingredients Work
Sweet potatoes and carrots get caramelized and sweet when you roast them hot enough. They don’t turn mushy either, which matters in a casserole. Zucchini and peppers add different textures and keep this from being too starchy.
Mushrooms are key. They soak up the oil and get crispy edges that taste kind of like bacon. White mushrooms are cheap and work fine. Cremini taste a bit richer if you want to spend more.
Cherry tomatoes go in last because they explode if you roast them with everything else. Adding them at the end means they stay whole and juicy instead of making everything watery.
Nutritional yeast tastes like cheese without being cheese. Sounds weird, works great. It’s got this savory, nutty thing going on. Paprika adds warmth.
The regular cheese sauce is flour, milk, and melted cheddar. Basic stuff. Full-fat cheese melts smooth. Low-fat works but gets a little grainy.
Essential Tools and Equipment
- Large rimmed baking sheet
- Parchment paper or cooking spray
- Large mixing bowl
- Medium saucepan
- Whisk
- Casserole dish (9×13 works perfectly)
- Sharp knife and cutting board
How To Make Roasted Veggie Casserole
Step 1: Preheat and Prep
Turn your oven to 450°F. Line a baking sheet with parchment or spray it. High heat is important here – that’s what makes the vegetables brown instead of just cooking.
Step 2: Prepare Vegetables for Roasting
Put all the vegetables except the cherry tomatoes in a bowl. Pour olive oil over them and add your seasonings. I use garlic powder, Italian seasoning, salt, and pepper but you can use whatever. Mix it with your hands.
Cut things about the same size. Doesn’t have to be perfect but if your sweet potato is in huge chunks and your zucchini is tiny pieces, they won’t cook at the same speed.
Step 3: Roast the Vegetables
Spread everything on the baking sheet. Don’t pile them up. They need space or they’ll steam. Put them in the oven for 25-30 minutes. Stir them every 10 minutes.
They’re done when they’re soft and have brown edges. Those brown bits are where the flavor is.
Step 4: Prepare Cheese Sauce
Make your sauce while the vegetables roast.
Vegan: Put all the ingredients in a pot and stir constantly over medium heat. Don’t leave it or it’ll burn on the bottom. Takes 5-7 minutes to get thick. It should coat your spoon.
Regular: Whisk the flour, milk, and cheese in a pot over medium-low heat. Keep whisking. Don’t stop. Takes 8-10 minutes. Add salt and pepper when it’s thick.
Step 5: Assemble Casserole
Turn your oven to 350°F. Spray your casserole dish. Put the roasted vegetables in, add the cherry tomatoes, pour the cheese sauce over everything.
Step 6: Final Bake
Bake for 5-10 minutes. This warms up the tomatoes and lets everything come together. Stir it before you serve so the sauce gets mixed in.
You Must Know
The vegetable roasting is what makes this work. Don’t cut it short. If your vegetables aren’t brown and soft after 25 minutes, leave them in longer. You need that caramelization or this is just bland vegetables with sauce.
Personal Secret: I make more vegetables than I need because I eat them right off the pan. Can’t help it. Also taste your cheese sauce while you’re making it. Every cheese tastes different, every nutritional yeast brand is different. Adjust as you go.
Pro Tips & Cooking Hacks
If your pan is crowded, use two pans. Crowded vegetables steam. You want them to roast.
Wait for your oven to actually reach 450°F before you put the vegetables in. That initial heat blast is what starts the browning.
Vegan sauce too thick? Add milk. Too thin? Cook it longer.
Regular cheese melts better if it’s not cold. Take it out while the vegetables roast.
Cherry tomatoes added early = watery casserole. Don’t do it.
Buy pre-cut vegetables if you’re busy. Nobody cares.
Flavor Variations / Suggestions
Italian: Add basil, oregano, parmesan.
Mexican: Use cumin and chili powder on the vegetables. Add cilantro and lime at the end.
Mediterranean: Throw in olives and sun-dried tomatoes. Top with feta and dill.
Smoky: Use smoked paprika. Drizzle BBQ sauce before baking.
Add Protein: Chickpeas, white beans, or leftover chicken work great.
Herbs: Fresh thyme, rosemary, or sage with the vegetables before roasting changes everything.
Make-Ahead Options
Roast the vegetables 2 days ahead. Keep them in the fridge. Make the sauce when you’re ready to eat.
Or assemble everything but don’t do the final bake. Cover it and refrigerate for 24 hours. Let it sit out for 20 minutes then bake at 350°F for 15-20 minutes.
Don’t freeze the whole casserole. The vegetables get watery. You can freeze just the roasted vegetables for 3 months though.
Recipe Notes & Baker’s Tips
Vegetables shrink when they roast. That’s normal. The water cooks out and the flavor concentrates.
Low-fat cheese makes grainier sauce. Full-fat is smoother. Your choice.
You can skip the final bake if you’re in a rush. Just mix everything hot and eat it.
This is perfect for using random stuff in your fridge. Got half a pepper? Use it. Some leftover chicken? Throw it in.
Serving Suggestions
Eat this as a main or a side. Goes well with bread, salad, grilled chicken, or rice.
Top with fresh parsley, basil, or chives. Add red pepper flakes if you want spice.
Good for potlucks or meal prep. Reheats fine. I usually make a double batch.
How to Store Your Roasted Veggie Casserole
Room Temperature: Don’t leave it out more than 2 hours.
Refrigerator: Keep it in a container for 4 days. Tastes even better the next day.
Freezer: Don’t recommend it. Vegetables get watery. If you freeze it anyway, it’ll last 2 months but the texture won’t be great.
Reheating: Microwave portions for 2-3 minutes. For bigger amounts, cover and heat at 350°F for 15-20 minutes. Add milk if it’s dry.
Allergy Information
Contains: Dairy (regular version), tree nuts (if you use nut milk)
Gluten-Free: Vegan version is gluten-free. For regular version, use gluten-free flour.
Dairy-Free: Make the vegan sauce.
Nut-Free: Use oat milk.
Vegan: Vegan sauce makes this plant-based.
Low-FODMAP: Skip onion and garlic. Use garlic-infused oil. Check your cheese.
Questions I Get Asked A Lot
My cheese sauce is lumpy – what happened?
Heat was too high or you stopped whisking. Keep it on medium-low and whisk the whole time. If it’s already lumpy, blend it.
Which cheese sauce do you prefer?
I like both. Vegan is lighter. Regular is richer. Depends on my mood.
The vegetables are cooking unevenly – help!
Cut them the same size. Don’t crowd the pan. Stir every 10 minutes. Rotate the pan if your oven has hot spots.
💬 Tried this recipe? Leave a comment and rating below! Tell me what vegetables you used.
