Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
Go here and click what's closest to your location. https://www.laff.com/find-us/ The stations in my region offer it over the air. I can also get Laff from my cable company via the Spectrum app. Your area might still be involved in an OTA channel "repacking" where they sold their frequency and moved to a different one. Rescan for OTA / antenna channels and see if your TV can pick up whichever local one offers Laff.
To the best of my knowlege, very few commercial networks are on Roku, due to licensing of each sitcom sport or show. If Laff is on Roku, it is not a legal feed, unless it is on your cable company's local feed or a pay IPTV app. Laff is on ALL Scripps TV stations, as it is owned an operated by Scripps. Not all TV markets will have this, just like other networks like COZI.