Basic Roux

The fat used in roux may be butter, shortening, lard, oil, or even
bacon drippings. Combine fat with an equal amount of flour; 1/2 cup
of each will make a good amount and any excess can be stored in the
refrigerator. (Many cookbooks call for a little more fat than flour -
2/3 cup oil to 1/2 cup flour is a common ratio.) Melt the fat in a
black skillet over low heat. When warm and fluid, sprinkle the flour
in a little at a time, stirring. Stir constantly until brown (this
may take 20 to 30 minutes); immediately remove from heat or add
ingredients your recipe calls for. If it burns even slightly, throw
it out and start over again.

Source: Rattray, Diana. "Recipes for gumbo, along with a basic roux."
About.com. February 7, 2009
<http://southernfood.about.com/cs/gumborecipes/a/gumbo.htm>;.