Preheat the oven to 325°F. Combine the first four ingredients in a bowl and set aside. In a small bowl, combine the spices and salt. Rub the spice mixture all over the roast.
Heat the oil in an ovenproof pot or Dutch oven set over medium-high. Add the roast and sear on all sides. Drain away excess fat, then pour in barbecue sauce mixture and bring to a simmer. Cover and cook the pork in the oven 3 hours, turning occasionally, or until falling apart tender. Remove the pork from the sauce, set in a large bowl and let rest 10 minutes. Set the sauce left in the pot aside for a moment.
After the pork has rested, pull into shreds with two forks or with your hands protected with kitchen gloves. Remove the fat from the surface of the sauce in the pot. Bring the sauce to a simmer over medium heat; add the shredded pork and mix to combine. Pile and serve the pork in the buns.