Place roast in a large greased slow cooker; season with next 3 ingredients. Add tomatoes with juice. Cover; cook on low 5½-6½ hours. Using 2 forks, shred beef and return to slow cooker. Spoon meat into taco shells or tortillas.
Tip: Make a build-your-own taco bar with black olives, green onions, shredded lettuce and more!