1Trim excess fat from pot roast. Cut meat in half and fit into bottom of crock pot cooker.
2Combine tomato sauce, onion, green pepper, brown sugar, Worcestershire, dry mustard, salt, and hot pepper sauce.
Pour tomato mixture over meat.
Tie pickling spice in cheesecloth bag; add to tomato mixture.
3Cover and cook on low heat setting for 10 to 12 hours, or until meat is very tender.
4To serve, turn to high heat setting. Lift pot roast and spice bag from sauce. Skim off excess fat. Remove meat from bone; discard bone and spice bag. Cool meat slightly; cut across the grain into thin slices.
When mixture in cooker bubbles, put cold water and flour into shaker; shake well. Blend into sauce mixture.
Return sliced meat to cooker. Cover and heat for 10 minutes. Fill hard rolls with meat mixture.