@Cloewen
That sounds like your Roku devices are going to low power mode, and your TV is not picking up any input on the HDMI ports. And that's normal.
Real quick, let me offer that it would be a better idea to hit HOME rather than OK to wake a Roku, or (here's where it's actually important) return it from screen saver. You'll see why shortly.
There is a setting on Roku for the screen savers, and in that area (Themes), you'll find a setting for the screen going black. Change the setting for Roku to not do that. Let the screen saver (there is a black screen saver option you can hunt for if you prefer that) run without putting the Roku in low power mode (the black screen).
Now, once the screen saver is always active, it can be awakened by any remote button (which is actually what you're already doing, if you think about it). If the button to awaken is the OK or Play button (you're using OK) then, if the screensaver includes ads (City Stroll and others have ads) and if the ad is the "active" item on screen, pressing OK will launch the ad. And the ad is probably for launching or installing an app. Home avoids that.
DBDukes
Roku Community Streaming Expert
Note: I am not a Roku employee.
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