Hi @Jamie_Lewis,
Thank you for sharing those screenshots. I am wondering if perhaps the Synology update reverted your Open vSwitch settings by any chance, see this thread: Lost my KEF LS 50 wireless connection [Solved - Synology had "Enable Open Vswitch" turned on]
This is possibly not related, but would be a good aspect to check next. Also, it appears that you have a workgroup of “WORKGROUP” set on the NAS, is there any change if you add this to the Roon IP config?