Cook flour in a Dutch oven over medium heat, stirring constantly, for 10 minutes or until golden. Remove flour from Dutch oven.

Coat Dutch oven with cooking spray. Sauté sausage over medium-high heat.

Add onions, celery, bell pepper, garlic, and ground red pepper; sauté 5 minutes.

Add chicken and sauté 3 minutes. Stir in flour until blended.

Gradually add chicken broth and tomatoes. Reduce heat to low, cover, and simmer 30 minutes.

Add shrimp and okra (if using); simmer 20 minutes.

Serve gumbo over hot cooked rice. Garnish with fresh celery leaves if desired.