Heat oil in large skillet or pot over medium high heat. Stir in flour; cooking until smooth and darkened to the color of a penny). Stir in next 11 ingredients (thyme - garlic) and cook until vegetables are tender (about 20-30 minutes -- my okra was still frozen when I added it, so it probably took a bit longer to cook than if I used fresh or thawed okra). Remove from heat and let cook for at least 30 minutes -- I did this part way ahead so mine cooled for over an hour.
In a large soup pot bring chicken broth, clam juice and reserved shrimp shells (don't forget the shells - they add lots of flavor) to a boil and then cook for 10 minutes or so. Remove shells and discard.
Stir in vegetable mixture into broth and cook until thickened over medium heat.
Stir in tomatoes, seafood (oysters - shrimp) and simmer 20-30 minutes -- but this can be kept warm over very low heat (I kept mine warm for over an hour and it was wonderful).
Serve over rice and sprinkle with green onions, if desired.