TV loses power when connecting to Roku

So, I do not have cable or satellite, and my TV is not smart. I have a Roku plugged into the HDMI port. As long as I turn the TV on (without the Roku plugged in) life is great. It will stay on the blank blue screen, but life is good. However, as soon as I plug the Roku in things go downhill. It stays on and appears to work for about 2-3 minutes, then all power is lost. The TV shuts off (or at least goes black) but there is no red standby light that comes on. The power button on the TV and on the remote are useless at that point. However, if the TV is unplugged and replugged the standby light returns and we are able to restart the process. I took the back off the TV last night (not sure what I expected to find). I’ve gone to settings on the TV and reset it. I’m so baffled. Is my Roku the problem? Is the TV the problem? Is it fix-able? Do I just need to give up and buy a new TV?