Cook the pasta. Cook the rigatoni al dente according to the package instructions. After cooking, drain it, then rinse with cold water to cool it off quickly and keep it from cooking more. Put it aside. Next, turn your oven on and set it to 400°F.
Prepare the ricotta mixture. In a small bowl, mix the ricotta cheese and dried oregano together. Set this mixture aside for later use.
Cook the ground beef. Heat the olive oil in a large, ovenproof skillet over medium heat. Add the ground beef and minced garlic, cooking until the beef is browned and no longer pink. If there is excess fat, drain it off before returning the beef to the skillet.
Make the sauce. Stir the salt, black pepper, crushed red pepper (if using), and tomato paste into the cooked beef. Then, cook for 2-3 minutes to allow the flavors to meld. Pour in the marinara sauce and crushed tomatoes, stirring well to combine. Bring the mixture to a boil, then reduce the heat to low and let it simmer for 10 minutes to allow the flavors to develop.
Combine the pasta and sauce. Remove the skillet from heat. Add the cooked rigatoni to the skillet, stirring to make sure the pasta is fully coated in the sauce. Sprinkle the grated Parmesan cheese evenly over the top. Dollop the ricotta mixture across the surface, then tuck the torn mozzarella pieces into the spaces between the dollops.
Bake the dish. Place the skillet in the preheated oven and bake for 15-20 minutes or until the cheese is melted and bubbling. Once done, remove the skillet from the oven and garnish with fresh parsley or basil. Serve immediately and enjoy!