Fanfoot the ROKU HDS cant do streaming we are talking about the new ROKU 2 which CAN do streaming and according to the Plex forums you can add the plex channel on the original ROKU and stream you media
It is true that the Roku 2 supports Plex, but then so did the older Roku boxes. I was simply saying that the Roku 2 doesn't natively support MKV streaming from a PC which was what the questioner asked. I understand that Plex is popular and does work, though my own experience with it on a Windows computer was less than stellar--it didn't support some files I tried and it crashed my computer regularly. So I uninstalled it. It would be better if it supported say DLNA natively. But hey, YMMV.