So mine keeps shutting off, but while I'm using it. Like I'll be partway through a show and it just shuts off and I get a message from the TV that says "no signal." When I do a hard reset it comes back, but shuts off again later on. It's all plugged in correctly and has been working perfectly up until this point.
Since this thread is 9 years old, suggest you open a new thread, but include information about which Roku device, including the model number.
for more tips on reporting issues.
Roku Ultra (4660), Roku 2 (4210), Roku Stick (3600)
Apple TV (4th gen), Fire TV, TiVo, Chromecast
Roku first, second, third, & fourth generation boxes.
Apple TV (2nd, 3rd gen)