Mix oil and flour in large saucepan. Cook over medium heat 6 to 8 minutes or until browned, stirring constantly. Add bell peppers, celery and garlic; cook and stir 4 minutes or until tender. Stir in salsa, tomato sauce and pepper sauce, if desired; simmer 10 minutes, stirring occasionally. Stir in shrimp; cook 6 to 8 minutes or until shrimp are cooked through. Top with green onions, if desired. Serve over rice.