From the Roku spec for JSON:
The URL of the video itself. The video should be served from a CDN (Content Distribution Network). Supported formats are described in Audio and Video Support.
That's not quite correct, you can use 301 redirects to the actually file. I had setup a redirect to mask the URL's from Vimeo and it worked fine for me.
This error is being caused by the Google Video platform. They, like DropBox won't allow you to stream to OTT/IPTV devices. You could probably write something to use their API to get the proper streaming URL's, but I'm not 100% sure about that.