Take a look at these tips for creating a Roux.Try This Technique:
Step 2. Cook over medium to medium-low heat, stirring constantly so the roux doesn't scorch.
Step 3. For a light roux, use butter instead of fat. Cook and stir for about 10 minutes. Light roux is light reddish-brown in color and is used to thicken cream and white sauces and light soups.
Step 4. A dark roux can be made with butter, drippings, or pork or beef fat. Cook for 15 to 20 minutes or until the roux is the color of chocolate. This dark, nutty-flavored base is essential for dishes like gumbo.