Cook tortellini according to package instructions. Set aside.
Prepare sauce by melting butter in a medium saucepan over medium-low heat.
Stir in flour, salt, and pepper and cook, stirring, 3-5 minutes.
Stir in milk; increase heat to medium and cook, stirring, until thickened and bubbly.
Stir in cheeses.
*If sauce is too thick, add more milk slowly until desired consistency is reached.
Stir in cooked tortellini, fresh spinach, and chopped artichoke hearts.
Season with salt and pepper as desired.