Well, using a JCAT NET Femto dual NIC card, one NIC has a fixed IP, the other is DHCP from the same network router. OS is Windows 2016 using their bridged mode.
Been using this setup with the second NIC direct to a Lumin U1 since day one. Works very well with Roon, why shouldn’t it, the same router supplies IP address on the same network, no subnets at all.