Add flour; cook over medium-high heat 2 to 3 minutes, stirring constantly, until sausage is coated with flour and lightly browned on edges. Stir in milk with whisk to completely combine. Heat to simmering, stirring occasionally. Reduce heat to medium; simmer 4 to 5 minutes or until thickened and until sausage is completely heated through. Add salt and pepper to mixture; stir to blend. Remove from heat; cover and keep warm.