Interesting talk about roux. I've had some formal cooking classes at CIA Hyde Park, NY, and we talked about the correct way to add roux, but I forgot and just wing it now. I do remember one time when I added some water to the roux, hoping to add that mixture to the soup, but that was not good. It was lumpy and I had to throw it out and make a new roux to thicken my soup. After that experience, I just add in small portions of the roux (usually warm, but not hot) to the entire batch of soup, and it dissolves very nicely.
As for measurements for roux, I just throw some fat or oil into the pan, and add flour slowly, until I get the consistency for which I'm looking. I learned that from my grandma.
The slow cooking is the only way to make a good roux. I usually heat the pan over medium heat to start, but after i stir in some flour, and the heat is up, I adjust the heat to low, and cook. Always make starting the roux the first thing you do. It will have plenty of time to cook while you peel shrimp, chop veggies, make stock, cook soup.
