Prepare the Eggplants: Preheat your oven to 375°F (190°C). Brush each eggplant slice with olive oil and season with salt and pepper. Arrange the slices in a single layer on a baking sheet lined with parchment paper. Bake for 15 minutes, until the eggplant is pliable and lightly browned. Remove from oven and let cool.
Make the Filling: In a mixing bowl, combine ricotta cheese, spinach, egg, garlic, nutmeg, salt, and black pepper. Mix well until all ingredients are evenly incorporated.
Assemble the Rollatini: Spread each eggplant slice with a generous amount of the ricotta mixture. Roll up the slices tightly and set aside.
Layer the Sauce: Pour half the marinara sauce into the bottom of a baking dish.
Arrange the Rollatini: Place the eggplant rolls seam-side down in the baking dish, on top of the sauce.
Top with Cheese: Sprinkle mozzarella and Parmesan cheese over the eggplant rolls.
Bake: Cover the dish with foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden brown.
Garnish and Serve: Let the dish rest for a few minutes before serving. Garnish with fresh basil leaves if desired.