Boil the noodles: Bring a large pot of salted water to a boil.
Cook the lasagna noodles until just shy of al dente, about 7–8 minutes. They should be flexible but not mushy.
Cool and separate: Drain and lay noodles flat on a lightly oiled baking sheet or clean kitchen towels. This prevents sticking and tearing.
Mix the filling: In a bowl, combine ricotta, 1 cup mozzarella, Parmesan, egg, garlic, Italian seasoning, red pepper flakes, parsley, and a pinch of salt and pepper.
Stir until smooth and well combined.
Prep the pan: Lightly oil a 9x13-inch baking dish. Spoon about 1/2 cup marinara sauce over the bottom and spread it evenly.
Assemble the rolls: Lay a noodle flat. Spread 2–3 tablespoons of the ricotta mixture evenly over the noodle, leaving a small border at the ends.
Roll up from the short end to create a tidy spiral.
Arrange in the dish: Place each roll seam-side down in the baking dish. Repeat until all noodles are filled and rolled.
Add sauce and cheese: Spoon the remaining marinara over the tops of the rolls. Sprinkle with the remaining mozzarella.
Add more Parmesan if you like.
Bake: Cover the dish loosely with foil and bake at 375°F (190°C) for 20 minutes. Remove the foil and bake another 8–10 minutes, until the cheese is melted and bubbly.
Finish and serve: Let the rolls rest for 5 minutes. Sprinkle with fresh parsley.
Serve warm with extra sauce on the side if desired.