In a large pot or Dutch oven, heat the vegetable oil over medium heat. Gradually whisk in the flour to create a roux. Cook, stirring frequently, until the roux is a dark chocolate brown color, about 20-25 minutes.
Add the chopped onion, green bell pepper, celery, and garlic to the pot. Cook for about 5-7 minutes, until the vegetables are softened.
Stir in the diced tomatoes, seafood stock, bay leaves, Worcestershire sauce, cayenne pepper, thyme, and oregano. Bring the mixture to a boil, then reduce the heat and let it simmer for 30 minutes.
After the gumbo has simmered, add the shrimp, crab meat, Andouille sausage, and okra. Cook for an additional 10-15 minutes, until the shrimp are opaque and cooked through.
Season the gumbo with salt and pepper to taste. Remove the bay leaves before serving.
Serve the gumbo hot over a scoop of cooked white rice. Garnish with fresh parsley and offer hot sauce on the side.