Peel the shallots and cut in half lengthways. Quarter the garlic bulb. Clean the zucchini and cut into 2 cm thick slices. Quarter and core the peppers and cut into 3 cm pieces. Wash the potatoes thoroughly and cut them into thirds. Remove the needles from the rosemary sprigs and chop them.
Mix the shallots, garlic, zucchini, bell pepper, potatoes and rosemary in a large bowl with salt, pepper and 5 tablespoons of olive oil.
Grease a baking sheet with 1 tablespoon of olive oil and spread the vegetables on top. Cook in the hot oven at 200 ° (convection 180 °) on the middle rack for 30 to 35 minutes. Remove the garlic and sprinkle the vegetables with 2-3 tablespoons of red wine vinegar and 2 tablespoons of olive oil. Let the vegetables cool slightly and season with salt and pepper if necessary. Roughly pluck the leaves from the basil stalks and mix in.