The HD PVR 2 does not have any linux drivers, yet. The HDMI cards that are supported under Linux are meant for editing purposes, and thus output a stream that is incompatible with being able to be piped directly into Xine/Mplayer/whatever.
As for the UIRT, I am sorry it went boom, you can probably send it back to Jon Rhees and he will fix it for you.
Another option for IR control is to use a GC100's IR outputs. There are 3 or 6 of them on a given GC100 device, and they work really well.
Another option is to get rid of IR control entirely. I have done this for both my living room and den setups, and my living room is controlled entirely by Ethernet, and the den TV is controlled via RS232. This is ultimately the more reliable approach.
As for streaming your roku, until we can get a reliable way to ship HDMI around the house via an H.264 stream, I would suggest looking into an HDMI switching matrix, and adding support for that. I will be going this route for my future house build.