I tried to download ROCK from this page: https://roon.app/de/downloads But what I downloaded was roon.dmg, the server for MacOS. Where can I find ROCK?
It looks as though you downloaded from the wrong link on that page. The ROCK download is actually elsewhere.
On the Download resources page, scroll down to the “All Roon downloads” section and expand the Roon Optimized Core Kit section - there’s a “download” link there:
This answer does not help because the problem is that this link does not lead to the download of this file. However, as I have now realised, only on the German page. I can’t access the English page because the system takes me by the hand like a toddler and decides that I must have wanted to see the German page, even if I enter the address of the English page. (I hate this kind of “supervised thinking”.) By changing the setting of my VPN, I was able to hide my origin and was then able to download the file.