Preheat the oven to 350°F. Line a large rimmed baking sheet or shallow roasting pan with parchment paper for easier cleanup.
In a large bowl, whisk together the olive oil, crushed garlic, basil, oregano, salt, and pepper.
Add the cubed eggplant, tomatoes, bell pepper, zucchini, and red onion to the bowl. Toss thoroughly to coat all the vegetables with the herbed oil.
Spread the coated vegetables out in a single layer on the prepared baking sheet, ensuring they’re not crowded (use two pans if needed).
Roast in the preheated oven for 30–40 minutes, stirring gently halfway through, until the vegetables are soft, caramelized, and lightly browned at the edges.
Remove from the oven and transfer to a serving bowl. Taste and adjust seasoning if needed. For extra flavor, drizzle with a little more olive oil or add chopped fresh basil or parsley.
Let the ratatouille rest for 3-5 minutes before serving warm, at room temperature, or chilled.