Pour broth and beer into a large slow cooker; add roast. Cover and cook on high setting for 4 hours, or on low setting for 8 hours, until roast is very tender. Remove roast from slow cooker. Shred roast with 2 forks and transfer to a roasting pan. Stir in barbecue sauce. Bake, uncovered, at 350 degrees for 30 minutes. Fill buns with pulled pork to make sandwiches. Makes 10 to 12 servings.