Preheat the oven to 180°C, 350°F, Gas Mark 5.
Cut the aubergines and courgettes into slices the thickness of a pound coin. Thickly slice the tomatoes. Halve and deseed the peppers, then cut into strips. Arrange the vegetables in a single layer in alternating rows in a baking dish.
Sprinkle over rosemary and seasoning then pour over the olive oil. Bake in the oven for 30-40 minutes until the vegetables are tender and golden. Remove from the oven.
Tear the mozzarella into pieces and scatter over the vegetables. Return to the oven for 5-10 minutes or until the cheese has melted. Just before serving scatter over torn basil leaves and drizzle over extra virgin olive oil.