Will Roon recognise music files stored on a USB stick/drive connected to the Meridian 210 unit and index them etc?
Can the 210 make the files available as a network share? If so, possibly. If not, no.
It certainly should do as far as I understand it. Though if you can connect your drive with the music to your core, it might be a less circuitous route.
I own a Meridian 210. It’s USB input is UPnP only. Roon will not ‘see’ an attached HDD.