I got it fixed on my Roku device without a single change to the build version. Posted info with Google and 2 hrs later it started working again without any new release of app version.
i am speculating that it was a SNAFU in the default YouTube admin settings that let channel content providers to disallow speed up options in the Youtube Roku app user interface. Most content providers do not care if their client subscribers speed up content at 1.25x-2.0x playback but some few do (since it reduces "airtime metrics" used by channel sponsors to reward fees per view-time. My content provider friends told me they did not disable any user fast play options so there was likely a systemic reset of defaults to "disallow" this feature recently by accidental glitch by a global Google/YOUTUBE administrator setting.
Hopefully this is now fixed for all.
