Preheat the oven to 190° C fan.
Clean & trim the vegetables; cut them in slices (except the red peppers: cut them in halves!).
Add some olive oil as well as salt & pepper & mix well w/ your hands.
Line a baking tray w/ baking parchment.
Arrange the vegetables on the baking tray & let them roast for about 30 min.
Peel the red peppers; then put all the roasted vegetables aside.
Grate the Parmesan.
Mix everything for the tomato sauce; optional: press the garlic & fold in.
Cut the mozzarella into slices.
Rub some olive oil on the bottom of the casserole.
Add some tomato sauce & put 2 lasagna sheets on top.
Add vegetables.
Add tomato sauce.
Add 2 more lasagna sheets & repeat ...
Finalize w/ 2 lasagna sheets & the rest of the tomato sauce.
Press all equally down.
Cover everything w/ mozzarella slices.
Bake in the preheated oven (190° C fan) for about 20-30 min.
If not 100% sure after 20-30 min just take a wooden stick & insert it in the lasagna - it should be totally soft ... (it’s like the test when baking a cake!).
Serve at once or let it rest ...