Preheat the oven to 180°C.
Toss chopped vegetables with 30ml of oil, salt, and pepper.
Roast vegetables on a baking tray for 15 minutes until softened.
Cut the top off the bread loaf to create a lid.
Hollow out the loaf leaving a 3cm shell and set aside the inner bread.
Pulse half of the removed bread into breadcrumbs using a food processor.
Mix remaining oil, vinegar, breadcrumbs, and garlic with the roasting juices.
Toss the vegetables in the liquid mixture and let stand for 60 minutes.
Slice the mozzarella and pat it dry with paper towels.
Spread pesto on the base of the hollowed loaf.
Layer vegetables, mozzarella, and torn basil until the loaf is full.
Replace the lid, wrap tightly in film, and chill overnight.
Slice the loaf into portions to serve.