Bring a large pot of salted water to a boil. Add the lasagna noodles and cook according to package instructions until al dente (about 8-9 minutes). Stir occasionally to prevent sticking. Drain and lay the noodles flat on a clean kitchen towel or parchment paper to cool.
In a large mixing bowl, combine the thawed and well-drained spinach, ricotta cheese, 1 cup of mozzarella, Parmesan cheese, egg, minced garlic, Italian seasoning, dried oregano, salt, and pepper. Mix thoroughly until creamy and well incorporated.
Preheat oven to 375°F (190°C). Spread about 1 cup of marinara sauce evenly on the bottom of a 9x13 inch baking dish. Lay one noodle flat and spread about 1/4 cup of the spinach and cheese mixture evenly over the noodle. Roll the noodle up tightly and place seam-side down in the baking dish. Repeat with remaining noodles and filling.
Pour remaining marinara sauce over the roll ups. Sprinkle the remaining 2 cups of mozzarella cheese on top. Cover the dish with foil and bake for 25 minutes. Remove foil and bake an additional 10-15 minutes until cheese is bubbly and golden.
Let the roll ups rest for about 5 minutes after baking. Garnish with fresh basil and parsley if desired. Serve hot with a side salad or garlic bread.