Heat 1 tablespoon olive oil over medium heat in a medium saucepan.

Add the diced onion and sauté until translucent, about 5–7 minutes.

Stir in crushed tomatoes, minced garlic, dried basil, oregano, and parsley.

Add a pinch of salt and pepper. Reduce heat to low, cover, and simmer for at least 20 minutes.

Stir occasionally.

Boil the lasagna noodles according to package directions until al dente.

Drain, rinse briefly under cool water to stop cooking, and lay flat on parchment or wax paper to cool.

Squeeze as much water as possible from the thawed spinach.

In a bowl, combine the drained spinach with 15 ounces ricotta, 1 1/2 cups shredded mozzarella, 2/3 cup Parmesan, and 1 large beaten egg.

Mix until uniform. Season with salt and pepper to taste.

Set oven to 375°F (190°C).

Spoon roughly 1/4 cup of the spinach-ricotta filling onto one end of each noodle, spreading into a rectangle but leaving the edges clear.

Starting from the filled end, roll the noodle tightly into a spiral.

Pour 1 cup of the tomato sauce into a 9 x 13-inch baking dish and spread to coat the bottom.

Place each roll seam-side down in the dish.

Spoon the remaining tomato sauce over the rolls and sprinkle the top with the remaining 1 cup of shredded mozzarella.

Bake uncovered for 25 minutes, until cheese is melted and the dish is hot and bubbly.

Let rest 5 minutes before serving to help the rolls hold their shape.