Currently my setup is like this
QNAP TS-879U-RP as Roon core with 4 network interfaces.
1 interface is being used for user data and also Roon Control and audio streaming to 2 RPI’s (1 Wifi, one cabled)
Works fine, but that interface is sometimes heavy loaded and giving some issues with audio playback.
My idea is to create a dedicated network for audiostreaming on 1 of the 3 “spare” Ethernet interfaces of the QNAP.
Control will remain on the first Ethernet interface as all my devices are using that network for data access and ofcourse Roon Control 
In the Settings => Setup interface of Roon I noticed that I could select the desired interface for Linn streaming which gave me the idea that it might work.
@support, can this concept work, control Rooncore from one interface while playback over another?
Thnxz
John