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. Wipe skillet clean.
Melt butter in skillet over low heat. Whisk in flour until smooth. Cook, whisking constantly, 1 minute. Gradually whisk in milk, and cook, whisking constantly, over medium heat about 10 to 12 minutes or until thickened and bubbly. Stir in sausage, salt, pepper, and, if desired, Italian seasoning.