@Alienwolf43
Sounds like someone (maybe innocently), is trying to mirror or cast to your Roku. Could be someone on your network (your home) or if you are using a shared network (motel/dorm etc).
If you have any little ones running around, they could also be using a mobile casting/mirroring app to do this.
Perhaps take a screenshot when this occurs next time and maybe can provide more info/help.
If none of the above applies, try resetting your Theme and Screensavers back to the Roku default ones in case an ad-supported screensaver is causing this issue. (Settings..Theme) and then just choose a default Roku Theme and a Default Wallpaper like the Aquarium or Clock.
To disable the ability to Screen Mirror, navigate to Settings..System..Screen Mirroring..Screen Mirroring Mode..Never Allow (or at least, Prompt)
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102