1. For the roux, in a heavy 2-quart saucepan stir together the flour and oil until smooth. Cook over MEDIUM-HIGH heat for 5 minutes, stirring constantly.
2. Reduce heat to medium. Cook and stir constantly about 15 minutes more or until a dark, reddish-brown roux forms. Cool.
3. In a 5-quart crockery cooker place water. Stir in roux.
4. Add sausage, chicken, okra, onion, sweet pepper, celery, garlic, salt, pepper, can tomatoes, and ground red pepper.
5. Cover; cook on LOW-heat setting for 6 to 7 hours.
6. Add shrimp and continue cooking on LOW heat for 20 minutes.