Preheat the oven to 180°C with the rack in the center position.
Bring a large pot of water to a boil over high heat and season with salt. Add the rigatoni and cook al dente according to package directions. Drain and store.
Meanwhile, in a large saucepan or oven over medium-high heat, add the sausage, ground beef, onion, and garlic and cook, breaking up the meat with a wooden spoon until tender. It’s cooked through and the onion is tender, about 10 minute minutes.
Add the marinara, chopped tomatoes, salt, Italian seasonings, and butter to the saucepan and cook, stirring frequently, until the butter melts and the sauce is fully incorporated into the meat (about 3 minutes).
Add the rigatoni to the sauce and mix.
Place the pasta and ragù on a 9×13 baking sheet. Mix the pasta with mozzarella, cover with aluminum foil and cook for 25 minutes. Remove pan from oven, cover and return to oven for an additional 10 to 15 minutes, or until cheese is lightly browned and sauce is bubbling.
Leave for 5 to 10 minutes. Serve sprinkled with parsley.