If you have a large music library you need to make sure you have the right equipment otherwise Roon can be slow.

If you have 8TB of music or less use an internal 8TB SSD drive in the sonicTransporter. Samsung drives are the best we have found.

If you have more than 8TB get a NAS. The NAS should have NVMe caching for speed. Otherwise Roon can be very slow.

Get a large NVMe cache cache 1TB - 2TB

The DiskStation DS720+ is one of the cheaper NASes that has NVMe cache. So that is what I recommend.

Here are the other Synology models with NVMe. Some have more disk slots and other features.
21-series DS1821+, DS1621xs+, DS1621+
20-series DS1520+, DS920+, DS720+, DS420+
19-series DS1019+
18-series DS918+