First step is to restart both your router/modem and your Roku devices. If the reset of the router does not work, then you will have to verify that the router's Wireless Settings (most likely Wireless Channel assignment is not properly configured or is configured to Auto Selection/Auto.)
2.4 ghz band (channels 1-11 with 1, 6, and 11 as default preferred, bandwidth 20mhz, mode/protocol g/n)
5.0 ghz band (channels 36-48 or 149-161, bandwidth 20mhz or 20/40, mode/protocol n/ac)
Post back if you need more help.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102