Preheat the oven to 200°C (390°F) using conventional oven settings (top and bottom heat). Clean the vegetables, cut the eggplant, zucchini, and bell peppers into approximately 2-centimeter (¾-inch) cubes. Peel and halve the onion, then cut it into slices about 0.5-centimeter (¼-inch) thick. Wash the cherry tomatoes.

Place the vegetables in a large bowl and toss with the olive oil, salt, and pepper. Spread the vegetable mixture evenly between two baking sheets and bake at 200°C (390°F) for 30 minutes. Remove the baking sheets from the oven halfway through the baking time and turn the vegetables over.

Meanwhile, put the ground meat, egg, breadcrumbs, and Parmesan cheese in a bowl, season generously with salt and pepper, and knead with your hands or a spoon until you have a homogeneous mixture. Form the meat mixture into 20 balls, each about 5 centimeters in diameter.

After 30 minutes, or when the vegetables are already tender, remove the baking sheets from the oven. Pluck the thyme leaves and add them to the vegetables along with the oregano, stirring well. Distribute the meatballs and gnocchi between the two baking sheets and return them to the oven for another 20 to 25 minutes, until the vegetables have a nice roasted aroma, the gnocchi are crispy on the outside and soft on the inside, and the meatballs are cooked through with an internal temperature of 70°C (160°F).

To serve, divide the oven-baked ratatouille among four plates and garnish with fresh basil as desired, or store any remaining portions in airtight containers in the refrigerator for up to 4 days after cooling.