They aren't on a roll, but Thangles come in strips and are the same deal as the ones on a roll.
Personally, I like the 8 at a time process. Fewest lines to draw and the HSTs come out with edges on the straight of grain.
http://www.generations-quilt-pattern...le-square.html
They have a link so you can download a chart on the size to cut your starting square to get the appropriate sized HST. I cut them a bit bigger & square them up using my Bloc Loc.