Funny how as soon as someone becomes a Roku employee you never hear from them again. Yes, @NB_ , I mean you!
who disturbs my slumber?
Komag, i don't think a game needs to worry about that - interacting with a game involves pressing keys, which keep screensaver away.
Regarding photo app - how does it sound the app implementing own screensaver? It will be called when app is running, after period of inactivity - instead of the system screensaver. It's a separate instance though, so the "main" app may have to communicate with the "screensaver" part via the registry they share or tmp:/