Mix red bell pepper, onion, and garlic in a large mixing bowl; season with basil, rosemary, salt, and pepper. Drizzle olive oil and balsamic vinegar over the pepper mixture; toss to coat the vegetables evenly.
Brush eggplant slices with olive oil to coat thinly.
Spread about 1/3 of the pepper mixture into the bottom of a square glass baking dish; top with a layer of about 1/3 of the eggplant. Repeat layering twice more. Top final layer with mozzarella cheese.
Bake in preheated oven until the cheese is browned and the vegetables are bubbling, 35 to 40 minutes.
All done! Now take a photo, rate it, and share your accomplishments!