What make/model TV? What Roku firmware version? . Once you reconnected your TV to your Roku account, it should have re-installed all of the channels you have on your account. You shouldn't have to do anything other than log back into the sites that need it.
Dan 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.