Bring a large pot of salted water to a rolling boil. Carefully add the lasagna noodles and cook them according to package instructions until al dente, usually about 8-10 minutes. Once cooked, drain the noodles and lay them flat on a sheet of parchment paper to cool.

While the noodles cool, prepare the spinach. Thaw the frozen spinach and squeeze out excess moisture using a clean kitchen towel.

Preheat your oven to 350°F (175°C). In a large bowl, combine the beaten egg, spinach, ricotta cheese, 1 cup of mozzarella, Parmesan cheese, salt, and pepper. Mix until creamy.

Spread about 1 cup of marinara sauce evenly across the bottom of a baking dish. Layer the filling over each noodle, then carefully roll them up tightly, placing them seam-side down in the dish.

Pour the remaining marinara sauce over the roll-ups and sprinkle with the remaining mozzarella cheese.

Cover with aluminum foil and bake for 30 minutes. Remove the foil and continue baking for an additional 5-10 minutes until the cheese is melted and golden.