I assume "it doesn't work" means you get no display at all on the tv screen.
Power outages, and returns from them, can be accompanied by surges that can damage electronics. It could be that your Roku was damaged, or maybe the tv, or both (or neither). Was everything powered via surge protected circuits?
You can troubleshoot by trying your Roku on a different HDMI port on the tv if it has more than one, to see if the problem is the tv's HDMI port. And ifbit doesn't work there it wouldn't hurt to try on a different set altogether just to make sure.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X | Streaming Stick 3600
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I have an ROKU Express and live in a rural area. Utility power drops are not uncommon here and can last from less than 1 second to several days. My approach with my computers, internet access and network attached storage are Uninterruptible Power Supplies (UPS) and a stand-by generator. While the generator may seem over-kill, mine will run our entire house, so life can go on over an extended outage. It also reduces the size of the UPS required because the UPS source is only required for about 20 seconds.
Having read these posts I will move the ROKU power source to one of my UPS units.