In a stockpot, melt butter over medium heat until bubbling. Add flour to make a roux, stirring constantly to prevent or remove any lumps. Cook the roux for 5 minutes. Do not brown.
Stir in onions and bell peppers; sauté for 10 minutes, or until onions are translucent. Add garlic and sauté for 3 minutes. Stir in crawfish tails. Slowly pour in enough water to reach a consistency that's a little thicker than soup. Season with cumin, Worcestershire sauce, hot sauce, salt, and pepper. Reduce the heat and simmer for 10 minutes.