I have put updates for the QNAP and Asustor NAS (which have been sent to QNAP App Center / Asustor App Central) on the roononnas.org website, for manual installation as long as they are not officially published.
It should fix the recurring authorization prompt after NAS reboot, introduced in Roon Server build 571.
Update #1 (30th June 2020):
Roon Server for ASUSTOR has been published to the ASUSTOR App Central.
Update #2 (10th July 2020):
Roon Server for QNAP has been published to the QNAP App Center.
Please update the Roon Server app from the corresponding App Stores to resolve the issue of having to reauthorise Roon Server after every reboot.