I turned the WiFi off in my Actiontec long ago. I have major heat issues with them, so it eases the load by removing that source of heat. Instead I have a router configured as a Wireless Access Point inside my home. This not only removes any issue with the Actiontec (which I think is a miserable piece of equipment) and gives me not only faster WiFi (5 GHz 802.11AC) but a 4 port Gigabit switch as well.
One possible problem might be if you have special characters in your wireless password, such as * & # or others. Roku doesn't seem to like those very well.
Nvidia Shield, Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.