Cut the eggplant, zucchini, bell pepper, and tomatoes into pieces and place them in a large mixing bowl.Finely slice the onion and add it to the vegetables.Drizzle generously with olive oil, season with salt and pepper, and mix well.
Arrange the vegetables on a baking sheet lined with parchment paper or in a large roasting pan.Distribute the garlic cloves among the vegetables, leaving them in their skins.Sprinkle with herbs.
Roast in the oven for 1 to 1½ hours, until the vegetables are thoroughly cooked.