In a large pot or Dutch oven, heat the vegetable oil over medium heat. Gradually whisk in the flour to make a roux. Stir constantly until the roux turns a deep brown color, about 20-30 minutes.
Add the onion, bell pepper, celery, and garlic to the roux. Cook, stirring frequently, until the vegetables are tender, about 5 minutes.
Stir in the sausage and chicken. Season with salt, black pepper, cayenne pepper, thyme, oregano, and bay leaves. Cook for another 5 minutes, allowing the chicken to brown slightly.
Slowly add the chicken broth and diced tomatoes to the pot, stirring to combine. Bring the mixture to a boil, then reduce the heat to low and let it simmer for about 45 minutes.
Add the shrimp to the pot and cook until they are pink and opaque, about 5 minutes.
Remove the bay leaves and discard. Stir in the cooked rice, parsley, and green onions just before serving.
Variations & Tips
For a seafood-only gumbo, you can omit the chicken and sausage and add more shrimp, crab meat, or even crawfish if you can find it. If you prefer a spicier gumbo, feel free to increase the cayenne pepper or add a few dashes of hot sauce. For a vegetarian version, skip the meat and use vegetable broth, and consider adding okra or mushrooms for extra texture. To save time, you can make the roux in advance and store it in the fridge for up to a week.
