There is a free public channel in the channel store called: Auto Launch. Works as a screen saver, can launch any channel installed on your Roku player. Information is located at: rokiosk.com/Autolaunch, Install it from AutoLaunch
I tried the AutoLaunch screensaver. Thought it was going to work but unfortunately is has some limitations that makes it unusable for me. One of my TVs would auto turn on after the 1 minute screensaver setting and would open to YouTubeTV (my selected channel). I had to disable the screensaver. It worked on the other TVs until this morning. The Roku menu showed on the TVs on powering on and the screensaver channel setting changed to ABCNews Live channel.
And I was unable to stream Spotify because essentially there is no activity in the Roku menu while streaming and after 1 minute, I was kicked out and the TV opened to YouTubeTV. It had potential but not for me.
Come on Roku, please add a setting to auto launch to a specific channel.