Cook sausage in a large skillet over medium heat, stirring until it crumbles and is no longer pink. Remove sausage, and drain on paper towels, reserving 1 tablespoon drippings in skillet.
Whisk flour into hot drippings until smooth; cook, whisking constantly, 1 minute. Gradually whisk in milk, and cook, whisking constantly, 5 to 7 minutes or until thickened. Stir in sausage, salt, and pepper.