Place roasts in an 8-qt Dutch oven; add water and salt. Cover and cook on medium-low heat for 2-1/2 hours or until meat is tender. Remove roasts and shred with a fork; set aside. Skim fat from cooking liquid and discard. Drain all but 1 cup cooking liquid. Add meat, ketchup, celery, steak sauce, sugar, vinegar and lemon juice. Cover and cook over medium-low heat for 1-1/2 hours. Serve on buns.