1. Add roast to a slow cooker and place potatoes and carrots around the beef.
2. In a small bowl, combine mustard, rosemary, thyme, salt and pepper and mix well.
3. Use a pastry brush to spread on the top of the roast.
4. Pour beef broth around the carrots and potatoes.
5. Cover and heat on low for 6-8 hours. Slice and serve.