4 tbsp flourPlace a frying pan or dutch oven over medium heat and heat the oil until just smoking. Whisk in flour, a little at a time and cook, whisking constantly, until roux becomes smooth and thick. Continue to cook, constantly stirring with a wooden spoon and reaching all over bottom of pan, until roux darkens to desired color. Be careful not to produce specs of black. The roux must remain an even color throughout process. If specs appear you must start over.
For a Light Brown Roux, cook the mixture, over medium heat for about 10-15 minutes, or until the color of peanut butter.
For a Medium Brown Roux, cook the mixture, over medium heat for about 15-20 minutes
For a Dark Brown Roux, cook the mixture over medium heat for about 20-30 minutes
NOTE: The timings for various shades of roux will vary depending on the cooktop as well as the amount of roux made. (A larger amount will cook in much more time.) If this is your first time making a roux, the slower you cook it, the less likely you will be to burn it. The important thing is to cook the roux to the desired color, as specified above.
Some of the above tips are taken from Emeril Lagasse