Preheat the oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.

Make the sauce: Heat 1 tbsp olive oil in a medium saucepan over medium heat. Add diced onion and sauté until translucent, about 5–7 minutes.

Add crushed tomatoes, minced garlic, dried basil, dried oregano, and dried parsley. Season with salt and pepper. Bring to a gentle simmer, cover, and reduce heat to low. Let simmer for at least 20 minutes.

Cook noodles: Boil lasagna noodles according to package directions until al dente. Drain and lay flat on parchment or wax paper to cool.

Prepare filling: In a bowl, squeeze excess water from thawed spinach. Mix spinach with ricotta, 1 1/2 cups shredded mozzarella, 2/3 cup Parmesan, and the egg.

Assemble roll-ups: Spread about 1/4 cup of the cheese-spinach mixture along each noodle, roll tightly. Pour 1 cup of tomato sauce into the prepared dish, arrange roll-ups seam-side down, then spoon remaining sauce over top.

Sprinkle remaining 1 cup mozzarella over the top.

Bake uncovered for about 25 minutes until sauce is bubbling and cheese is melted. Let rest 5 minutes before serving.