Mom's Shrimp Creole

This is a dish I grew up eating and always loved. I will admit that, when I was little, I'd pick out the shrimp and eat only the sauce. However, my taste buds have changed quite a bit (as my mom ALWAYS used to tell us they would!) The beauty of this dish is that it is SO full of flavor, yet it's pretty simple. It does involve making a roux, but I think it's the perfect place to start if you've never made a roux before, since it's a light roux, as opposed to a time-consuming, labor-of-love dark roux. My mom grew up in Alabama, so she has a great repertoire of southern recipes and this is one that we always looked forward to eating. It's great served over a big bowl of rice with fresh french bread and a salad.
3 lbs raw shrimp, peeled and deveined
2 tbsp vegetable oil (typically, you would use 1/4 cup, but I've found that you can cut back on the fat without a problem)
1/4 cup flour
1 cup diced onion
1 green bell pepper, diced
1/2 cup diced celery
2 cloves garlic, minced
16 oz tomato sauce
1/2 cup water
1 tsp salt (or creole seasoning)
1/2 tsp sugar
1 tsp Worcestershire sauce
1/2 tsp black pepper
1/2 tsp Tabasco
2 tbsp chopped green onions

Heat oil in a pan on medium-high heat. Add the flour and stir continuously until it reaches a light, golden brown color. It should smell nutty. Add the onions, bell peppers, garlic and celery. Cook until tender. Add all remaining ingredients, except shrimp and green onions. Cover and simmer gently for 30 minutes, stirring occasionally. The sauce will be pretty thick. Add shrimp and cook an additional 15 minutes or until shrimp are cooked through and sauce has thickened back up (the liquid from the shrimp thins it a touch at first). Serve over rice. Serves 4 (generous size portions or 6 smaller portions)