Cook pasta according to package directions.

In a large sauce pan, melt butter over medium heat. Sprinkle in flour and stir until smooth.

Increase heat to medium-high, slowly add milk while stirring constantly.

Bring to a boil, while continuing to stir, boil for 2 minutes, or until thickened.

Remove from heat and stir in cheese.

Add drained pasta and season with salt and pepper.