Mix tomatoes, onion, garlic, wine, fennel, oregano, salt, and pepper in labeled gallon freezer bag. Add raw pork; remove excess air and seal.
Before cooking, promptly freeze flat on tray up to 2 months. Keep pasta and Parmesan separate.
Thaw bag on rimmed tray in refrigerator 24 to 48 hours until no ice surrounds pork. Empty into 6-quart slow cooker; discard bag.
Cover; cook on low about 8 hours until pork at least 145°F and easily shredded. Lift out; remove remaining visible fat and pull into strands.
Skim excess sauce fat; return pork. Boil rigatoni according to package, about 10 to 12 minutes. Reserve 1/2 cup cooking water; drain.
Toss pasta with ragu; loosen with reserved water a tablespoon at a time if needed. Divide among 6 bowls; add Parmesan.
Refrigerate leftovers within 2 hours. Reheat in covered saucepan with spoonful of water, stirring, to 165°F in center.