@Chuck_Nelson you will need to remove the application and all supporting files from the mini before reinstalling Roon. The instructions below should be helpful:
However, first you should create a backup of Roon on your old MacBook which you used for your Roon Server. Open Roon on the MacBook and then create a backup from within Roon’s Settings → Backup and use that backup file to restore Roon on the mini so you don’t lose any of your Roon settings and history.