I have the same issue, yet I know how to fix it on all the devices throughout my house except Roku. I need to install the root certificate for my network in the trust certificates for each device. Yet no such place or method exists to do this with YouTube on Roku. Google/YouTube use HSTS and therefore require the root certificate to be present to be able to connect. Any ways to enable this Roku?
I'm now having the same issue. YouTube is the only affected channel.
There's no way to install certificates on a Roku device. An app can use its own, but there's no way to install one for all apps or any specific app.