I believe Roon advocates moving the heavy processing (in form of Roon Core) away from the listening room. This helps reduce EMI/RFI from NAS to affect the audio equipment.
You said you have a switch that feeds six rooms, so I suppose it’s possible to find another room to place your Synology without needing very long Ethernet and DC cable.
If you can hear a difference with footers added to the NAS, I’m afraid your audio equipment is sensitive to vibration, especially tube amp and some types of capacitors.
Additional CPU load can also have an effect on the NAS fan. So people go through the trouble to make their Roon Core fanless, including Roon Nucleus and SonicTransporter.