You only use it for Roonserver? Doesn’t matter then, I don’t know where the library is stored but you’ll need to have a crazy library to get anywhere near even the 15GB use of the smallest partition (swap is a backup for your memory, not storage)
For performance it makes no difference, they are all the same drive anyway.
I see, my /var directory is 22Gb big for 220.000 files. When I do not make an separate /var directory, where is the /var located then? in /home of in /root?