Place roast in a 5- or 6-qt. slow cooker; sprinkle evenly with soup and dressing mixes. Add broth and Worcestershire sauce. Cook, covered, on low until meat is tender, 6-8 hours., Remove roast from slow cooker. Skim fat from cooking juices; keep warm. Shred beef with 2 forks; serve in tortillas with toppings as desired. Serve with juices for dipping.