Cook sausage in a large skillet over medium heat, stirring often, 7 minutes or until browned. Remove sausage; drain and pat dry with paper towels.
Heat oil in a stainless-steel Dutch oven over medium heat; gradually whisk in flour, and cook, whisking constantly, 18 to 20 minutes or until flour is caramel-colored. (Do not burn mixture.) Reduce heat to low, and cook, whisking constantly, until mixture is milk chocolate-colored and texture is smooth (about 2 minutes).
Increase heat to medium. Stir in onion, next 4 ingredients, and, if desired, ground red pepper. Cook, stirring constantly, 3 minutes. Gradually stir in chicken broth; add chicken and sausage. Increase heat to medium-high, and bring to a boil. Reduce heat to low, and simmer, stirring occasionally, 1 hour and 30 minutes to 1 hour and 40 minutes or until chicken is done. Shred chicken into large pieces using 2 forks.
Stir in shrimp; cook 5 minutes or just until shrimp turn pink.
Place Roasted Potatoes in serving bowls. Spoon gumbo over potatoes. Serve immediately with desired toppings.