Preheat oven to 350 degrees F. Bring a large pot of salted water to a boil.
Place a large skillet over medium heat. Add ground beef and onions. Cook until beef is cooked through and onions have softened, about 10 minutes. Break up the meat as it cooks.
Drain grease from skillet and add garlic. Cook for about 1 minute, until fragrant.
Add crushed tomatoes and 1/2 tablespoon of Italian seasoning. Stir and bring to a boil. Reduce heat to medium-low and simmer sauce while pasta cooks.
Add lasagna noodles to boiling water, stir, and cook until al dente according to package directions. Drain and run under cool water to stop the cooking.
Place thawed spinach in a double layer of paper towels or in a kitchen towel. Squeeze out all the excess moisture you can. Place spinach in a mixing bowl with ricotta 1 cup mozzarella, 1/2 cup Parmesan, egg, salt, and 1/2 tablespoon Italian seasoning. Stir until evenly combined.
Grab a 9-inch x 13-inch baking dish. Spoon enough meat sauce into the bottom of the dish to have a good layer.
Lay pasta out on a flat work surface. Divide spinach mixture evenly over each of the noodles, and spread to cover the surface. Roll up the noodles, starting at the short end. Place seam side down into the prepared baking dish. Repeat with remaining pasta and arranging in the dish to make them all fit.
pour remaining meat sauce over the lasagna roll ups. Sprinkle the top with the remaining mozzarella and Parmesan cheese.
Bake for 30 minutes until the filling is bubbling and the cheese has melted.
Remove from oven and let rest 5-10 minutes before serving. Spoon extra meat sauce over roll ups as needed. Sprinkle with chopped parsley for garnish.
Notes
You can prep this recipe all the way up to the point of baking and then cover with foil and store in the fridge or freezer for later. If you freeze the roll ups, defrost them in the fridge overnight before baking.