Roll opens her mouth and begins to draw in air, immediately noticing that only her butt seems to be expanding, much to her amusement. "Hehe, not really an unexpected place for garbage, but it's certainly a very interesting one." she thinks to herself as she allows her rear to fill up with air and lots of other things.
Needless to say, Roll is more than happy to use her new function to completely clean up the lab, thankful that she didn't lose too much mobility due to the built-in anti-gravity function that came with the cartridge. Her butt does become too large to get through even the bigger passageways, but by that time her task is completed and she is more than satisfied.
At this point, each side is at least twice her size. The actual garbage is compressed into one-foot wide spheres, one in each cheek. Roll has no problem rolling back on her rear so that she's 'sitting' on it. "Hehe...once again I have my own couch!" Roll says, as she begins to wonder about something. "Now...what exactly am I going to do with this junk I've got in my trunk?" she ponders as she reads through the manual to figure out what happens to the garbage that gets collected.