Preheat the oven to 375°F (190°C). Lightly oil a 9x13-inch baking dish or coat it with a thin layer of marinara.

Cook the lasagna noodles in a large pot of salted boiling water until al dente per package directions. Drain and lay flat on a clean kitchen towel to cool slightly.

In a medium bowl, stir together the spinach, ricotta, shredded mozzarella, Parmesan, egg, salt, and pepper until well combined. Taste and adjust seasoning.

Spoon a generous strip of marinara over the bottom of the prepared baking dish to prevent sticking and add flavor.

On a flat surface, place one noodle. Spread about 1/8–1/6 of the spinach mixture evenly along the noodle, leaving the edges clear.

Roll the noodle tightly from one short end to the other and place seam-side down in the dish. Repeat with remaining noodles.

Pour any remaining marinara sauce over the rolls. Sprinkle extra mozzarella on top if you like a cheesier crust.

Cover the dish tightly with foil and bake for 25 minutes. Remove the foil and bake another 10–15 minutes until the cheese is melted and bubbly and edges show light browning.

Let the rollups rest 5 minutes before serving so slices hold together.