Combine tomatoes, onion, garlic, wine, fennel, oregano, salt and pepper in a labeled gallon freezer bag. Add raw pork chunks, remove excess air and seal.
Freeze before cooking: lay flat on a tray and freeze promptly for up to 2 months, keeping pasta and Parmesan separate.
Thaw the bag on a rimmed tray in the refrigerator for 24 to 48 hours until no ice remains around the pork. Empty into a 6-quart slow cooker and discard the bag.
Cover and cook on low for about 8 hours until pork reaches at least 145°F and is tender enough to shred easily. Lift the meat out, remove remaining visible fat and pull into strands.
Skim excess fat from the sauce and return pork to it. Cook rigatoni in boiling water according to the package, about 10 to 12 minutes; reserve 1/2 cup cooking water before draining.
Toss pasta with the ragu, loosening with reserved water a tablespoon at a time if needed. Divide among 6 bowls and sprinkle with Parmesan.
Refrigerate cooked leftovers within 2 hours and reheat in a covered saucepan with a spoonful of water, stirring, until the center reaches 165°F.