Preheat oven to 160°C (140°C fan-forced). Remove rind from pork; reserve. Season pork. Peel and quarter brown onions.
Heat oil in a large flameproof casserole dish over high heat; cook pork and onions, turning, for 5 minutes or until pork is browned on both sides. Add ginger beer and vinegar to dish; bring to the boil. Cover with a tight-fitting lid.
Roast pork in oven for 3 hours, turning pork once. Remove lid; roast for a further 30 minutes or until pork pulls apart easily. Remove pork from dish; cover with foil.
Place dish with roasted onion and pan juices on the stove to high heat; bring to the boil. Cook for 10 minutes or until reduced and thickened. Using two forks, shred the pork; stir through the sauce.
Assemble coleslaw following packet instructions. Split bread rolls. Fill rolls with coleslaw and pulled pork.
Pork and sauce suitable to freeze. Not suitable to microwave.