I've had my roku for a little over a year and it had worked well before. I just turned it on for the first time in a few months and it will not show any networks. it just says "no networks found". I restarted it a few times and nothing has changed. I know for a fact there are plenty of wifi networks around me.
I am having the same problem with my Roku express.
I'm having the same problem as well connected working well until I had a power outage and that's when it begins saying no network I reset my TV unplug my tv from both ends and still no success I am at a point I don't even know what to do.
I've found that when I've encountered wifi problems with my Rokus I've normally been able to solve them by restarting the router. After the router comes back up, restart the Roku (Settings > System > System restart) to start with a clean slate and try to reconnect.
This makes no sense to me and I don't understand why it would work, especially since other wifi devices in the house work well, but it has worked for me on several occasions.