That address is what happens when a device cannot get an address from the DHCP server. Did your router go poof? Try rebooting a bunch of stuff (router, switch, wifi, modem, etc.) then reboot Roon Core and see if it gets a proper address.
Ken, @ipeverywhere gave you the answer. The IP address of your Rock is not in the same IP range as the rest of your system. Until you get everything back on the same network you will not be able to resolve your problem. Do you know hw to check the IP address of the various devices in your system? In my system everything is on a network with the address that begins: 192.168.1.XXX. You need to resolve this before you will be able to listen to music via Roon.
The 169.254.X.X address space is link-local. It may work, but it may have issues.
This explains it a bit more. You may wish to set up your network in RFC 1918 address space.