What is your router model number and who is your ISP (internet service provider)?
It is usually a wireless channel settings issue with the 5ghz band (using DFS channels 52-140) which are not compatible with Roku. If this is the issue, then need to Disable DFS usage at router or manually use non-DFS channels (36-48, or 149-161) in the 5ghz Wireless settings in router.
However, you should be able to connect to the 2.4ghz band if your ISP has not disabled your 2.4ghz ability.
Provide some more details what is occuring and hopefully can get you back up and running.
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