In addition, SSD reads data without generating vibration and is supposed to give less electric noise that compromises SQ.
Yes, although as I understand it, this isn't an issue if you're only using an HDD for local library storage with Roon (and not as the location where Roon Core is installed). In Roon's storage settings, you set a path to the device. Then Roon continually monitors it for new files. When it finds them, it integrates them into your Roon library. In that scenario, I don't believe Roon goes back to the HDD to read the data for real-time playback (again, assuming Roon Core is not installed to that HDD).