Melt butter, or heat oil in a sauce pan over LOW heat.
Add flour, and whisk to combine.
Bring mixture to a simmer and allow to barely simmer for 2 minutes.
Pour in hot beef drippings or stock and whisk to combine.
Continue heating, stirring occasionally until gravy thickens. Do not boil or gravy will break {separate} and you will have to start over.
Season to taste and pour into a gravy boat or bowl. Serve while hot.
Notes
The more flavorful your Pot Roast, the more flavorful your gravy! All of the wine, beef drippings, and vegetable flavors will end up flavoring your gravy.
If you do not have a roast, you can always use a good quality beef stock and add some seasonings as needed.
Do not walk away from the stove, you do not want the gravy to boil.