Here is the problem I see with the roux, you are using way too much flour with the oil/fat. It should be no more than a 50/50 mix of flour and oil/fat, even the original recipe of 2 cups flour to 1 3/4 cups oil I disagree with. Never more than a 50/50 mix, sometimes I go a little more oil than flour but not by much.
I make my roux in a cast iron Dutch oven and like what was said in another post, once you start the roux you never and I mean NEVER leave the pot unattended. If you walk away just to even open a beer, the roux is ruined, it will burn, it has to be stirred constanly. Make sure you have everything ready to stand by the pot stirring constantly for about 30 minutes to make a good dark roux.
I start off with a medium heat seating, your stove may be different, mine is gas. If there is any slight evidence of smoking, reduce the heat immediately, I cannot stress this point enough because it will cause the roux to burn. As my roux darkens I keep my heat setting between medium and medium low, the darker it gets the more I reduce the heat to prevent burning the roux.
Roux takes practice, I know, I've ruined many of batches of roux trying to get it right. Keep practicing and you'll get it right too.
