1.In a medium saucepan of 2 1/2 cups water and 1 teaspoon salt, cook rice according to package instructions ; set aside.
2.While rice is cooking, heat vegetable oil in a large stockpot or Dutch oven over medium heat, add sausage, and cook, stirring frequently until sausage is lightly browned, about 5 minutes; remove from pan and set aside.
3.Add onion, bell pepper and celery. Cook, stirring occasionally, until tender, about 5 minutes.
4.Stir in tomato paste, garlic and Cajun seasoning until fragrant, about 1 minute.
5.Stir in red beans, chicken stock, hot sauce, bay leaf and sausage; season with salt and pepper, to taste. Bring to a boil; cover, reduce heat and simmer for 20 minutes.
6.Remove from heat, remove bay leaf and stir in rice until well mixed.Cover and let sit for 10 minutes.