I just started h aving this problem. I re booted the roku and the router twice, unplugged the roku twice, etc. etc. I do not understand the other steps you recommend -- those seem to be for modern computer geeks and are in a language I don't understand. How about simple steps, e.g. should I buy a new ROKU and will that resolve the problem?
If the affected device is either a Roku Express or Roku Premiere, please note that they are only compatible with wireless b/g/n networks on the 2.4 GHz spectrum. Ensure that your router is broadcasting a 2.4GHz Wi-Fi network for the device to connect to. You can check your device model by navigating to Settings > System > About.
You can also try configuring your router and use wireless channels 1, 6, or 11 which are the preferred channels in North America. Each time you change the wireless channel, you will likely need to apply/save changes before you are prompted to restart the router.