01 - Preheat oven to 375°F (190°C). Lightly grease a 9x13-inch (23x33 cm) baking dish.
02 - Cook lasagna noodles in a large pot of salted boiling water until al dente, following package directions. Drain and lay noodles flat on a clean towel.
03 - In a large bowl, combine ricotta cheese, 1 cup of mozzarella cheese, Parmesan cheese, drained spinach, egg, nutmeg, salt, and black pepper. Mix until smooth and well combined.
04 - Spread 1 cup of marinara sauce on the bottom of the prepared baking dish. Lay out a lasagna noodle, spread approximately 3 tablespoons of the ricotta-spinach mixture evenly over the noodle, and roll up tightly from one end to the other. Place the roll seam-side down in the baking dish. Repeat with remaining noodles and filling.
05 - Pour the remaining marinara sauce evenly over the rolls and sprinkle the top with the remaining 1 cup of shredded mozzarella cheese. Cover with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
06 - Allow to stand for 5 minutes before serving. Garnish with fresh basil leaves, if desired.