there's no risk with Shimano rotors, after running them for years I'm quite happy to have my life depend on them. it's true the ice tech isn't beneficial to trials but they are slightly lighter, I'd still just use the standard non ice tech though personally.
I also agree with Mark, if you're using a brake that has quite deep pads (Mono trials) then I'd get a rotor with a braking surface big enough for all the pad to hit otherwise the brakes not going to be getting it's full potential power.