In a large skillet, over medium heat, melt the butter. Whisk in the flour and let it cook, stirring occasionally, for about a minute to cook out the floury taste.
Turn the heat up to high and stir in the half and half, a little bit at a time, adding more each time the mixture thickens and comes back together. Once it's all incorporated and the mixture's begun to thicken a bit, reduce the heat to medium again.
Stir in all of the remaining ingredients EXCEPT the tortellini, until the cheese is completely melted and the spinach has begun to wilt slightly.
Toss the cooked tortellini into the creamed spinach mixture until evenly coated.
Serve as is, or reduce the heat to low and stir occasionally, while you prepare the shrimp.