Preheat your oven to 375°F (190°C).
Brush each eggplant slice with olive oil on both sides and place on a baking sheet lined with parchment paper. Bake for 15 minutes until soft and pliable.
In a mixing bowl, combine the ricotta cheese, half of the mozzarella cheese, Parmesan cheese, egg, garlic, oregano, salt, and pepper. Stir in the fresh spinach until well mixed.
Spread a thin layer of marinara sauce on the bottom of a baking dish.
Take one eggplant slice at a time and place about 2 tablespoons of the spinach and ricotta mixture on one end. Roll up tightly and place seam side down in the baking dish.
Repeat with the remaining eggplant slices and filling.
Pour the remaining marinara sauce over the rolled eggplants.
Sprinkle the remaining mozzarella cheese on top.
Bake in the preheated oven for 25 minutes, or until the cheese is bubbly and golden brown.
Let it cool for a few minutes before serving. Garnish with fresh basil leaves.