Begin by bringing a large pot of salted water to a boil. Once boiling, carefully add 12 lasagna noodles and cook them until al dente, about 8-10 minutes. Drain the noodles and immediately cool them under cold running water to stop the cooking process. Lay them flat on a clean kitchen towel to keep them from sticking together while you prepare the remaining components.

In a large skillet over medium heat, add 1 pound of ground beef, along with 1 diced onion and 3 minced garlic cloves. Cook until the beef is browned and the onions are soft, approximately 5-7 minutes. Season with salt, black pepper, and 1 teaspoon of dried oregano before stirring in a 24 oz jar of marinara sauce. Let this simmer gently for 5 minutes.

In a mixing bowl, combine 15 oz of whole milk ricotta cheese, 1 large egg, ½ cup of grated Parmesan cheese, and 1.5 cups of shredded mozzarella cheese. Add a handful of freshly chopped parsley and mix until well incorporated.

Spread a thin layer of meat sauce across the bottom of a 9x13 inch baking dish. Take a cooked lasagna noodle and spoon a line of the ricotta filling along one end. Gently roll the noodle up and place it seam-side down in the baking dish.

Pour the remaining meat sauce over the rolled lasagna noodles, ensuring they are well covered. Sprinkle the remaining 1.5 cups of shredded mozzarella cheese evenly over the top. Cover the baking dish with aluminum foil and bake in a preheated oven at 375°F for 40 minutes.

After baking, remove the foil and broil the lasagna roll ups for an additional 3 minutes. Allow the dish to rest for 5 minutes before serving.