I seem to remember that I did not get the tallest, but I don't remember for sure. They might have had 8' or 10' rolls. Don't know if the store ceilings are high enough for the largest rolls they have online (12').
You could call and see what they have in stock: 202-898-0555
By the way, they have discounts for some arts groups. For example, I think DC Arts Center members get 20% off.