There is only one download now for Roon for Mac (or Windows) as the both the server and controller components (which can now be run independently) are installed.
I would recommend rebooting your Mac then downloading and installing Roon. It’s helped a few other users that have reported this issue.
Also check out this post …
Hope it helps, but if not Roon support or someone familiar with MacOS than myself will be along to offer further assistance.