Hi Mike
Roon cannot take a signal from the NDX2, it can only play from the Roon Core (Tidal, Qobuz or locally stored files) to a Roon ‘Endpoint’.
Other than that are loads of Roon ready streamers that would work here. If you still want Naim multiroom as well the best option would be an ND5XS2 which makes an excellent digital transport via its SPDIF out.
Thanks Chris, I had wondered about that as an option and would probably use the ND5XS2 straight into the SN2 in that scenario. It then raises the inevitable question, is the cost worth it for a third system compared with the Uniti2 line out into the SN2 - I’ll probably start with trialing that for free