It is so dumb and twisted that there even needs to be a deal. Any web browser can hit youtube, you can probably get to youtube via a web browser anyway on a roku, if not they could in principle do that. Also dumb and twisted that as a paying youtube subscriber, I could buy a computer (a roku) and not be allowed to access youtube on it. Do better, tech.
I find it more annoying that standard websites don't just work on a Roku. I'd rather Google didn't have to maintain yet another app for yet another proprietary device, it should all just be build on open standards.
As a workaround, when a video provider is not supported on Roku, what I do is stream video directly from my Android phone to Roku using a free app which is available on both platforms. It is not as convenient as having a dedicated Roku app, but it works.