Preheat the oven to 300°F with a rack in the center position.
In a large Dutch oven, (or in a slow cooker) combine the chicken stock and vinegar. Nestle in the pork and sprinkle with the brown sugar, mustard powder, garlic powder, onion powder, chili powder, salt, pepper, and cayenne.
Cover and roast in the oven for about 3½ to 4 hours. Uncover and roast 1 hour more, or until the pork is tender and can be pulled apart easily with a fork. If using a slow cooker, cover and cook on low for 8-10 hours or cook on high for 4-6 hours.
Using a slotted spoon, transfer the pork to a large bowl or baking dish, discarding any large pieces of fat. Use two forks to shred the pork into 1-inch pieces.
Serve the pulled pork on the rolls and top with as much bbq sauce as you like. Store in an airtight container in the refrigerator for up to 1 week.
