In a large bowl, combine ground beef and ground pork, breaking them up with your hands. Add breadcrumbs, Pecorino Romano, eggs, milk, garlic, parsley, salt, and pepper, and mix gently just until combined.
Scoop and roll the mixture into balls about 1 1/2 inches wide. You should get roughly 18 to 20 meatballs.
Heat the cast iron skillet over medium-high with a thin film of olive oil. Working in batches, sear the meatballs on two or three sides until browned, about 5 minutes per batch, then set aside.
In the same skillet, brown the sausage links on all sides until deeply colored, about 6 minutes, then transfer to a plate.
Season the pork ribs with salt and pepper, then brown them in the fat until a crust forms, about 8 minutes total, and move them to the plate.
Add olive oil to your Dutch oven over medium heat, then stir in the diced onion and cook until soft and translucent, about 6 minutes. Add the garlic and cook for 1 minute more.
Add the tomato paste and stir constantly for a full 2 minutes until it darkens to brick red. Pour in the red wine, scraping up browned bits, and let it reduce by half, about 3 minutes.
Crush the whole San Marzano tomatoes by hand as you add them, then stir in the crushed tomatoes. Add Italian seasoning, oregano, red pepper flakes, salt, and black pepper, then drop in the Parmesan rind if using.
Taste, and only if the tomatoes are sharp, stir in a pinch of sugar to round out the acidity.
Nestle the browned sausage and pork ribs into the gravy along with any juices from the plate. Bring to a gentle bubble, then lower the heat to the barest simmer and partly cover.
Cook for 2 1/2 hours, stirring every 30 minutes and scraping the bottom so nothing catches.
Gently lower the browned meatballs into the gravy and tuck in the fresh basil leaves. Simmer uncovered for a final 30 minutes, so the meatballs cook through and the gravy thickens.
Fish out the Parmesan rind, taste, and adjust the salt.
Boil the rigatoni in well-salted water until al dente, following the package timing. Drain, then toss the pasta with a few ladles of the gravy.
Plate the pasta with more gravy on top and the meats piled alongside, then finish with grated cheese and basil.