In a large pot, bring 8 cups of water to a boil, then add the smoked turkey tails. Let them simmer for 45 minutes to create a flavorful broth. Reserve 4-6 cups of this cooking liquid for later use.

While the turkey is simmering, chop the onion and bell pepper into 1/2-inch pieces, and chop the celery into 1/4-inch pieces. Mince a tablespoon of garlic to enhance the flavor.

In a separate pot, heat vegetable oil over medium heat and whisk in the all-purpose flour. Cook for 15-20 minutes, stirring constantly until the roux reaches a deep chocolate brown color.

Add the chopped onion, bell pepper, and celery to the roux. Cook for about 5 minutes, stirring frequently, then add the minced garlic and cook for an additional minute until fragrant.

Stir the reserved turkey, its cooking liquid, and chicken broth into the roux and sautéed vegetables. Add the Creole seasoning and Rosamae seasoning salt, then bring to a gentle simmer before reducing to low heat for about 1 hour.

Carefully mix in the sliced smoked sausage and frozen collard greens, allowing them to simmer for 45-60 minutes, or until the greens are tender.

Add the large shrimp into the pot during the last 10 minutes of cooking to ensure they remain tender. Before serving, sprinkle in the gumbo file powder and stir well.

Taste, adjust seasonings as needed, and serve your delicious gumbo over fluffy white rice.