I am not that familiar with the Roku, but it should be able to use a playlist file (.m3u) with links to all the channels. To build the playlist, the easiest thing to do would be to create a favorites list (bouquet) with all the channels (or a few separate ones) and then in openwebif under Television->Bouquets if you select the little TV icon, you can download the whole bouquet as a playlist. Then in an editor, you can replace all the ip addresses in the playlist with the no-ip address and it should be usable from outside.
The downside is it would not have an epg (although the Roku may pickup now/next from the stream)
Others may have a better solution...
