First, to see if you can get the RokuTV to connect to your network again, try rebooting your router and also unplugging your RokuTV. Then plug the TV back in. See if the combination of rebooting the router and the unplugging now gets you connected to your network. If so, you should now be able to use either your Roku mobile app as a remote or attempt to pair your Roku remote.
If the above does not work, try to connect your TV to a mobile hotspot if available. Once you connect to your hotspot, should be able to get the Roku remote to pair as well. If you have two phones available, use one as the hotspot and the other to use the Roku mobile app remote feature.
If practical, the third method would be to run an ethernet cable to the RokuTV from your router if your RokuTV has an ethernet port available. This should give you a wired connection immediately.
If you have the Roku Voice remote, you should be able to push the pairing button (look in the battery compartment for a little button and press it until it flashes green) and then unplug your RokuTV. Plug it back in and press the manual On button located on the RokuTV.
If your Voice Remote does not have a pairing button, then press and hold the Home and Back buttons for 5 seconds and look for a light to flash on the top left front of Roku Remote. Then unplug your RokuTV. Plug it back in and press the manual On button located on the RokuTV.
https://support.roku.com/article/360011621473 (pairing Roku remotes)
If still having issues, try posting a screenshot here or posting model number of the remote you are having issues with. (to post screenshot, look for the little camera icon above.)
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941