Preheat the oven: Start by preheating your oven to 400°F (200°C). Prepare a sheet pan by lining it with parchment paper or lightly greasing it to prevent sticking.
Prepare the vegetables: In a large mixing bowl, combine 1 medium diced eggplant, 1 medium sliced zucchini, 1 chopped red bell pepper, 1 chopped yellow bell pepper, 1 cup halved cherry tomatoes, and 1 chopped onion. These vegetables are the stars of the dish!
Add flavor: Drizzle 3 tablespoons of olive oil over the mixed vegetables. Add in 3 minced garlic cloves, 1 teaspoon dried oregano, 1 teaspoon dried basil, and salt and pepper to taste. Toss everything well until the veggies are evenly coated with the oil and seasonings.
Spread on the sheet pan: Transfer the seasoned vegetables onto the prepared sheet pan, spreading them into a single layer to ensure even roasting.
Roast: Place the sheet pan in the oven and roast for approximately 25-30 minutes. Halfway through the cooking time, stir the vegetables gently to allow for even caramelization.
Finishing touches: Once roasted, check the vegetables to ensure they are tender and caramelized to your liking. Allow them to cool slightly before serving.
Garnish and enjoy: For added flavor, garnish with fresh basil before serving. Enjoy your delicious ratatouille hot, warm, or even at room temperature!