Roon had to update some foundations and your outdated macOS does not support these anymore, because it is end-of-life by Apple.
You can temporarily reinstall Roon version 2.64, which works with your outdated macOS. The download link is in the release notes:
You will then need to make sure to deactivate automatic updates in Roon Settings > About.
Then make sure you have a safe Roon database backup on a different device (such as an external USB drive).
Going forward, you need macOS 12 (Monterey), but most old Intel Macs that don’t get the update from Apple can easily be updated with Open Core Legacy Patcher (OCLP):