I swear to fucking Stallman, this is at least the fourth time this past week I've seen a unique post about this same fucking shit. One dude writes an article going "xrandr let's you rotate the screen 22 degrees" and the holiday tech news cycle just loses its mind.
This is called Automatic Content Recognition and it can be disabled in the settings, highly recommend doing that. It should have asked you whether you wanted it enabled when you set up the TV, as it's legally required to be opt-in in the US opposed to opt-out. Since you're using a Roku Smart TV, it specifically is taking two full resolution "video snapshots" every second.