In culinary school you will find that a sauce is one of 5 components that makes up a recipe. The other four are; cooking method, ingredients, aromatic and seasonings. So learning to make a good roux is important not only to the flavor of your food but can also save you money and be beneficial to your health.
Let take a jar of a well known Alfredo sauce in the store. Not only do you not know how long it's been sitting around on the shelf, the ingredients are;
Why do you want all those chemicals when you can make your own Alfredo sauce with 5 ingredients? You need to start with a white sauce. Your fat is melted butter, remember as you melt the butter you don't want it to separate, make sure to keep it yellow next add in the flour a little at a time to make a paste. Cook out the proteins means to keep it on a low heat until it bubbles and turns white. If you smell a nutty smell the proteins are cooked out. This process prevents the sauce from becoming lumpy. Next add cold milk and stir until thickens add in the garlic (2 cloves, minced) and gradually add in the Parmesan cheese (1 1/2 cups) until melted. Other recipes exclude the flour and use 1 cup whipping cream instead.
You can even make gravy from roux.