Cut roast in half and place in a 3- or 4-qt. slow cooker. In a small bowl, combine the ketchup, brown sugar, barbecue sauce, Worcestershire sauce, mustard, liquid smoke if desired and seasonings. Pour over beef.
Cover and cook on low for 8-10 hours or until meat is tender. Remove meat; cool slightly. Skim fat from cooking liquid.
Shred beef with two forks; return to the slow cooker. Cover and cook for 15 minutes or until heated through. Using a slotted spoon, place 1/2 cup on each bun. Serve with onions, pickles and jalapenos if desired.