I had a Roku, and found it to be almost worthless. It is only good if you have streaming Netflix or Amazon Prime. For anything else you are limited to whatever channels they want to offer, and usually with very poor/low resolutions. There is a media streaming application, to stream video from your computer, but it is only for Windows, not Linux. I was so disappointed in Roku, that I gave away three of them that I had purchased.
With my HTPC, I can get much more streaming video, including Flash video. And I can watch sporting events vis ESPN3, which the Roku can't do.