PS3 Media Server tries to be an UPNP A/V Media Server, or DLNA server. I could not find if the Roku SD or HD are a typical UPNP A/V Media Renderer, so I will assume the are not.
It looks like you can add "private channels" via the SDK you have stated. If that is the case, then somebody needs to create a DLNA client for the Roku. Some people have done something similar to that, but still not right: http://forums.roku.com/viewtopic.php?f=28&t=25955
I would suggest to ask in the Roku forums.