With everything dropping off your network like that, i would suspect you have a network configuration or an actual router problem (could be failing) Especially since some of your devices are using your 2.4gz (Express and Premiere) while your RokuTV and Roku Sticks are capable of using both your 2.4gz and 5gz. If network was working even somewhat properly, something should be seeing something,
Reboot your router. Try plugging your Roku Stick power into wall, not your TV USB. Then try setup again.
You may have to access your router's configurations settings. Do you know how? Are other wireless devices connecting to your network ok?
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