Thanks for letting us know about the issue that you are experiencing.
For assistance to set up your Roku remote to control your TV volume and power, visit our Support pages here:
How do I set up my Roku® enhanced remote to control my TV?
Why is my Roku® enhanced remote not controlling volume and power on my TV?
If you are still not able to resolve your issue with those troubleshooting steps, please send me a PM with your Roku account email address, and include the serial number of the Roku device from Settings>System>About. I'll be able to assist you further from there.
The same thing has happened to me. It happened very suddenly. I have had the Roku device for about 10 months. When I power up the TV, and then try to get the Roku home page, it flashes up for 1 second, then disappears into a black screen. I have tried unplugging the TV to RESET, and also have tried unplugging the ROKU device to to RESET and neither of these things have worked. Was some kind of a software update done and now the device doesnt work? HELP! I dont want to have to go out and buy a new ROKU.
I suggest starting with new batteries in the remote. Then just for programming the remote have it so the remote can see both roku and the front of the tv, maybe attach it to side hdmi for now, or if you have hdmi coupler have at the end of regular hdmi cable. Now try and program it for your tv, if it isn't controlling the roku either, re-pair and then program it for your tv.
Believe me no one has programmed roku remotes more for TV's then I, and with roku behind the tv set out of line of sight you get more fails then having line of sight to roku at least during programming.
Sounds like what my tv was doing. Posts in a different thread gave me a solution. When the screen goes black, try changing the picture mode on your TV remote. It works for me but I am still hoping Roku will fix it properly.