There's two usual causes of this (Roku does not add random apps in spite of what some people think):
- There's a forgotten Roku device (or known Roku device) linked to the same Roku account.
- A screensaver that advertises content is being used and improperly dismissed.
In the case of 1, be aware that Roku devices linked to the same Roku account will have the same installed apps. If someone is adding an app to a device it will show up on all devices linked to the same account.
In the case of 2, pressing Play/Pause (and possibly OK) will install whatever app is currently being advertised on the screensaver. Don't press Play/Pause when the screensaver is active. Press any other button to dismiss the screensaver before pressing Play/Pause.
Note that Roku also advertises on the main Home Screen menu on the left and pressing Play/Pause while on the menu will probably do something you didn't want.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.