Get a couple cans of glow in the dark spray paint (found mine at Fred Meyers) and paint a patch of wall. It'll be pretty much invisible on a white wall, even in the dark unless it's under direct light for a long time. Then get some UV LEDs (found some on amazon.com... might be able to find them other places. We've gotten a few from liquidemotions too but they were kinda pricey.) Now draw on said wall with light! It's super awesome, even if you're not rolling, but while rolling your motions feel super smooth and drawing in itself just seems cool.
If you can't do that, even some of those kiddie glow-in-the-dark art kits would be super cool. Or just some paper and markers.
Oh, funny story! One of my friends was drawing on a piece of paper while rolling and seemed to fall asleep. When she "woke up" again the page was covered in writing and pictures, song lyrics, inner thoughts, ect that she couldn't remember doing!