Ma Cher.... It's easy!!!
Put one part oil (Vegetable, Corn, Canola, ect...) and All Purpose Flour in a heavy pot (Holds the heat)... Put the oil in first and heat then add the flour and sir or whisk in.... I use a large wooden spoon as not to damage my black iron pot, it's easier with a flat utensil... Continuously stir.. you can go a minute or two rest, but just don't let it sit... Then it depends on how much roux you need... to cook for 4 or 5 people, I'll do about 3/4 cup of oil and flour and I might not use it all.