Prepare the Zucchini: Use a mandoline or sharp knife to slice zucchini lengthwise into thin strips. Aim for about 1/8-inch thickness to ensure they roll easily.

Make the Filling: In a large bowl, combine the ricotta, half of the mozzarella, Parmesan, egg, and Italian seasoning. Mix until well incorporated.

Assemble the Roll-Ups: Lay out each zucchini slice, spread a spoonful of the ricotta mixture on top, then roll up the slice. Repeat until all zucchini slices are used.

Arrange in Baking Dish: Place each roll-up seam-side down in the dish. Pour marinara sauce over the top, ensuring all roll-ups are covered. Sprinkle the remaining mozzarella cheese evenly over the dish.

Bake and Serve: Bake in the preheated oven for 25 minutes or until the cheese is fully melted and golden. Remove from the oven, garnish with fresh basil, and serve immediately.