Combine first 11 ingredients in a large bowl. Add pork roast, turning to coat with marinade. Cover and refrigerate roast at least 4 hours or overnight.
Remove roast from marinade, reserving marinade. Brown all sides of roast in hot oil in a Dutch oven. Add reserved marinade.
Bake, covered, at 275° for 6 to 7 hours or until meat can be shredded. Garnish, if desired.