Either epoxy or super glue gel, depends on the size of the scroll. If its already rather large I would use epoxy and super glue gel and use cable ties to help hold it in place while the epoxy drys. Once dry Id cut the cable tie. If the piece isnt too large or heavy I'd just use straight super glue gel. Most LFS sell both types of glue, and usually both are available at home depot as well, I am pretty sure HD has an epoxy labeled for aquarium use.
HD carries Aquamend, which is a 2 part epoxy and is reef safe. Suprisingly, mighty putty works as well and IME is reef safe. The only problem is that epoxy is not that good for securing corals or things that cannot have pressure kept on them while they cure. I suggest super glue gel for such applications.
