I think what he's looking for the is width and height of the source video itself that is streaming, rather than the specified size of the video player window playing the video stream.
I don't know of a way to get that info on the roku side unless it has been pre-specified in the content feed and parsed into the content node before display (ie running ffmpeg or mediainfo on the server, having the source resolution in a database, or manually specified in the xml or json feed for the channel).
There isn't a corresponding roVideoMetaData to correspond or accompany the roAudioMetaData component.