Sprinkle the beef with 1 teaspoon salt and ½ teaspoon pepper and place in the bottom of a 6-quart slow cooker.
Pulse the onions in a food processor until finely minced, about 15 pulses, scraping down the sides of the bowl as needed. Transfer the onions to a large bowl and stir in ¼ teaspoon salt. Cover and microwave for 5 minutes. Drain onions in a fine-mesh strainer, pressing with a rubber spatula to extract excess liquid. Return the drained onions to the now-empty bowl.
Process the pancetta, salami, carrot and celery in the now-empty food processor until ground to a paste, about 45 seconds, scraping down the sides of the bowl as needed. Transfer the pancetta mixture to the bowl with the onions. Stir the wine, water, 2 tablespoons of the olive oil, tomato paste, oregano, ¾ teaspoon salt and ½ teaspoon pepper into the onion mixture until thoroughly combined.
Pour the onion mixture over the beef in the slow cooker, covering the beef with the mixture. Cover and cook until the beef is fully tender, 8 to 9 hours on low (or 5 to 6 hours on high).
Bring 4 quarts of water to a boil in a large pot. Add the pasta and 1 tablespoons of salt and cook, stirring often, until al dente. Reserve ½ cup of the cooking water, then drain pasta.
Using a potato masher, mash the meat until coarsely shredded into bite-size pieces. Stir in the Romano cheese and the remaining 2 tablespoons olive oil. Transfer the pasta to the slow cooker and stir to combine with the sauce. If too thick, thin the sauce with the reserved cooking water as needed. Season with salt and pepper to taste and serve.