On a large baking sheet, arrange the onion, bell peppers, and chicken sausage. Drizzle with olive oil and season with 1 tablespoon Creole seasoning, or to taste. Using your hands, mix everything together well.
Bake for 8 minutes, or until chicken sausage begins to brown.
While the vegetables and chicken sausage are cooking, place the shrimp in a small bowl. Season with 1 teaspoon Creole seasoning and ½ teaspoon paprika. Stir to coat.
Remove the vegetables and sausage from the oven, and add the seasoned shrimp and diced tomatoes. Mix everything together.
Return everything to the oven for 6 minutes, or until the shrimp is just done.
Remove from the oven and add the cooked rice, mixing everything together well.
Garnish with sliced scallions and serve immediately.