Preheat your oven to 375°F (190°C). Cook the lasagna noodles according to the package instructions until they are al dente. Once cooked, drain and lay them flat on a clean kitchen towel to prevent sticking.
In a large skillet, heat the olive oil over medium heat. Add the finely chopped onion and sauté until it becomes translucent, approximately 3-4 minutes.
Add the minced garlic and sliced mushrooms to the skillet. Cook until the mushrooms are softened and have released their moisture, about 5-7 minutes.
Incorporate the fresh spinach, dried oregano, salt, and black pepper into the skillet, cooking until the spinach wilts, which should take around 2-3 minutes. Remove the skillet from heat and allow the mixture to cool slightly.
In a mixing bowl, combine the cooled mushroom-spinach mixture with ricotta cheese, half of the mozzarella cheese (1/2 cup), and half of the grated Parmesan cheese (1/4 cup). Stir well to fully blend the ingredients together.
Spread a thin layer of marinara sauce on the bottom of a 9x13 inch baking dish to create a base for your rolls.
For each lasagna noodle, spoon about 2-3 tablespoons of the filling onto one end of the noodle and roll it up tightly. Place each roll seam-side down neatly in the baking dish. Repeat this process with the remaining noodles and filling.
Once all the rolls are in the dish, pour the remaining marinara sauce evenly over them to ensure they are well covered. Sprinkle the top with the remaining mozzarella cheese and the remaining grated Parmesan cheese for a delightful cheesy crust.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Remove the foil and continue baking for an additional 15 minutes, or until the cheese is bubbly and golden brown.
Allow the lasagna rolls to cool for about 5 minutes before serving to enhance the flavors.
Notes
Serve garnished with fresh basil or parsley and a side of mixed greens.