Suggestion : Would love feature to Play sound and have screen turned off.
I have that feature on HIsense Android and use that daily . Miss that feature
I have this feature on a low end JVC tv in our guest bedroom that is prone to screen ghosting (this forum won't let me call it b*urn-in, how weird!). It's nice to use when playing a music channel, and helps avoid ghosting for the static visual displays on some of them.
I think this has to be a TV feature and with all the EnergyStar stuff I don't how it's not a requirement. About all a Roku could do is turn the screen black which isn't the same thing as turning off the display, but it may be better than nothing. I created a black/blank screensaver years ago, but so many music streaming channels override the set screensaver that it's not all that useful.