In a large saucepan- melt butter, take off heat and stir in flour till no lumps. Then return to medium heat stirring approximately 10 minutes until dark (browned). Stir in celery, and onions, cook 10 minutes.
In a bowl, mix tomato paste and stock. Stir into cooked mix. Add tomatoes, shrimp, and seasonings. Cover and simmer 20 minutes on medium heat - stir occasionally.
Serve with rice. If you use the crabmeat, put it in on the plates at the last minute otherwise it will cook to shreds in the pan.