Quick answer is no, since the technology behind Youtubes urls & domains doesn't give the ability to use Youtube as a video hosting platform for creators of Roku channels. Therefore, the only way to use YT videos would be to download & host them elsewhere, which would be a violation of YT's terms & conditions.
Even putting that aside, it's still probably a violation or bending of the rules of YT or Roku's ToS. One could make the analogy of running a Facebook page & sharing YT vids on it, but I think this is a step further and Roku has different ToS than FB.
FWIW, YT obviously does have the proper, backend url to self host, but they do not make the publicly available even to the user who's account it is.
