This is a very unofficial how-to. I could probably be arrested by the French government for even calling this a tutorial. But this is how I make roux and it works just fine for my purposes.
First off, a roux is a cooked mixture of flour and fat, usually used as a thickening agent in cooking. I use it for one of two reasons: to thicken a soup or to form the base of a sauce (usually a cheese sauce for pasta). If I am making any type of creamy soup, I make a roux to whisk in during the last half hour of cooking. It gives the broth a thicker, velvety texture that I love, without changing the flavor.
Let me know if you thicken anything exciting!
I am at the craft fair today and tomorrow, so I'll share some pictures of that later in the week!