Your not playing the MQA version from Roon here at all just regular flac, Roon offers all versions of albums to play. It would say it was MQA in the signal path of it was. What tier are you subscribing to is this set correctly in Roon, check the versions tab of the album and select the MQA version.
Then I suspect you have the wrong tier set in Roon or its not recognising you have hifi plus. What tier do you subscribe to? Hifi only gives you MQA that is 16bit nothing above that will play as MQA. If your on Hifi Plus then it will play all versions of MQA. Check what you have Tidal service set to in Roon. Change it if needed, sign out then back in again and see if it helps. If not then raise a support ticket giving all your details.
MQA files play perfectly on Rose streamer via Tidal iPhone app.
Been in extensive conversation with Rose agent in UK - they see no issues with the hardware. Seems increasingly like a Roon issue. Any further suggestions?
In addition to the things you were already advised to check but apparently have not (or at least not confirmed in the thread), also check that you have the new MQA preference setting configured correctly