i spent a few weeks putting together a simple control app for the roku for osx, as there didn't seem to be any mac clients around. it allows you to browse the library, queue files and select from the now playing queue and play radio presets only (this is all i use the roku for).
you can get it here:
hope it is useful for someone.
ps i think it will only work on 10.6, used a few new apis [/url]