Cook the lasagna noodles according to package instructions until al dente. Drain and lay them flat on a clean surface to cool.
In a mixing bowl, combine the ricotta cheese, chopped spinach, 1/2 cup mozzarella cheese, grated Parmesan cheese, egg, garlic powder, salt, and pepper. Mix until well combined.
Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish, about 1/2 cup.
Take a lasagna noodle, spoon a generous amount of the cheese and spinach mixture onto one end, and carefully roll it up to enclose the filling. Place the roll-up seam-side down in the baking dish. Repeat with remaining noodles.
Once all roll-ups are in the dish, pour the rest of the marinara sauce over the top. Sprinkle with the remaining mozzarella cheese.
Cover the dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Let it cool for a few minutes before serving. Garnish with fresh basil leaves if desired.