The original Prismatic Roper was a weird beastie from the 3.5 Monster Manual III, that never seemed to get any playtime in any modules I read. When I was designing the Meridianese Pirate's shift Mines, I knew I wanted a zone much like the AD&D Quasi-Elemental Plane of Minerals, and wanted to stick some of these odd things in there.
Here are the stats I made up for them. I'll warn you now, we had a near TPK, with the party fleeing (in a manner) from the battle, so be prepared for these things to kick ass.
As always, you need to add half the monster's level (rounded down) to the stat modifiers listed. As the original monster was not in the SRD, I'm hoping I'm not breaking any rules by publishing this....if I am, and anyone gets upset, I'll take it down of course!