You could never win the World Championship Gumbo Cookoff in New Iberia with a store bought roux....they don't allow it.
I have been fortunate to win the amateur division milange category twice back when I worked with LandCoast.
Sig, you are right about cooking a roux of that size....but nobody says you cant have a beer at 6am!
My take on the roux, I love to make it from scratch because one of my best and most favorite smells in the world is when you bring the roux to the brink of burn and throw in your fresh chopped veggies to cool it down.
Just my thoughts and smells!