Melt butter in a large saucepan or Dutch oven over medium heat.
Whisk in flour and cook, whisking constantly, until roux is a light caramel color, about 5 minutes.
Add onion, green pepper, and celery and cook, stirring frequently, until vegetables are just tender, about 8 minutes.
Add garlic, salt, pepper, garlic powder, onion powder, cayenne, oregano, and thyme and cook, stirring constantly, until fragrant, about 1 minute.
Stir in stock, tomatoes and Worcestershire sauce and bring to a boil.
Reduce heat to low to maintain a simmer and cook, uncovered, stirring occasionally, until the vegetables are very soft and the sauce thickens, about 20 minutes.
Add crawfish tails and simmer until heated through, about 5 minutes.
Stir in parsley and scallions.
Divide mixture among 4 serving plates or bowls and serve with rice.
Garnish with more parsley and scallions.
