"If it has no roux, it's a soup." That's straight from my Cajun bride [6]
Actually all you need to make great roux is a properly working oven! My wife makes roux the old fashioned stovetop way, buy my mother-n-law bakes it in the oven and it works out great. If interested I could probably cough up the recipe.[<)]
When visiting my wifes family (Lake Charles, La) we hit the bayou for a while and go crabbing with chicken necks first. That's because for proper gumbo you need about a doz. cleaned blue crab bodies floating around the top of the gumbo pot!