For the Meatballs

For Sauce and Pasta

For the meatballs: Mix meat, bread crumbs, cheeses, eggs, oregano, parsley, and salt and pepper to taste in a large bowl. Gently shape mixture into 12 1 3⁄4" meatballs, cover with plastic wrap, and set aside.
For the sauce: Bring a medium pot of water to a boil. Add sausages and boil for 5 minutes. Drain and set aside. Put oil and onions into a large wide heavy pot and cook over medium heat, stirring often, until onions are soft, 8–10 minutes. Add garlic and cook briefly, then stir in crushed and diced tomatoes, basil, oregano, parsley, and salt and pepper to taste.
Submerge meatballs and sausages in sauce in pot and bring to a simmer. Reduce heat to medium-low, cover, and simmer, stirring occasionally, for 1 hour. Partially uncover pot and continue to simmer, stirring occasionally, until sauce is deep red and has thickened, about 1 hour more. Transfer 2 of the sausages and 2 of the meatballs to a medium bowl and mash them up with a fork. Return meat to pot and stir to combine. Adjust seasonings.
Cook pasta in a large pot of boiling salted water until just tender, 8–12 minutes. Drain pasta and return to pot. Add half the sauce to the pasta, toss well, and divide among four to six plates. Put sausages and meatballs into one dish and the remaining sauce into another to be passed around the table. Garnish pasta and meat sauce with additional grated cheeses, if you like.