01 - Preheat your oven to 375°F (190°C).
02 - Cook lasagna noodles according to package directions until al dente. Drain and lay flat on a clean towel.
03 - In a mixing bowl, combine ricotta cheese, spinach, Parmesan cheese, egg, basil, minced garlic, nutmeg, salt, and black pepper. Mix until smooth and well incorporated.
04 - Spread ½ cup of marinara sauce evenly across the bottom of a 9x13-inch baking dish.
05 - Arrange each cooked lasagna noodle and evenly distribute 2–3 tablespoons of the ricotta-spinach mixture over the surface of each noodle.
06 - Tightly roll each noodle and place them seam-side down in the prepared baking dish.
07 - Pour the remaining marinara sauce evenly over the top of the rolled noodles.
08 - Sprinkle shredded mozzarella cheese and the remaining grated Parmesan cheese over the sauce.
09 - Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and continue baking for an additional 10–15 minutes, or until the cheese is bubbly and golden brown.
10 - Allow the dish to rest for 5 minutes before serving.