Ok, I think I have sorted it out.
In Roon I named the Meridian USB2 ASIO Driver to be System Output and disabled WASAPI.
Things are now working as expected.
I am offering this as I don't expect I will be the first one with limited computer skills to be stuck here.
Cheers Chris


No 18 in the Hall of fame smile I have simple tastes; I am content to settle for the best:
GIK monster bass panels, rear wall. QNAP TVS 471i3. Roon into DSP5200SE via 210/ 218 zone... Explorer 2. Bluesound Pulse 2, Mini & Flex. 596v1, 518, Foxsat HD, Sony BDP, Pioneer 5090, 2 Chromecast's for LRB videos. MS200 to F80 for a Roon zone