In a large pot, bring salted water to a boil and cook the lasagna noodles according to package instructions. Drain and set aside to cool slightly.
In a medium bowl, combine the chopped spinach, ricotta cheese, half of the mozzarella cheese, 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 and set aside.
Take each lasagna noodle and spread a generous spoonful of the cheese and spinach mixture evenly on top. Carefully roll the noodle from one end to the other.
Place each rolled lasagna seam-side down in the prepared baking dish. Repeat with remaining noodles and filling.
Once all the rolls are in the dish, pour the remaining marinara sauce over the top and sprinkle with the remaining mozzarella cheese.
Drizzle with olive oil and cover the dish with aluminum foil. Bake in the preheated oven for 25 minutes.
After 25 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.
Remove from the oven and let it cool for a few minutes before serving. Garnish with fresh basil leaves if desired.