Signalyst’s NAA needs a few updated libraries from Debian Stretch that are not present in Debian Jesse – you’ll see the needed dependencies when you try to install the NAA in DietPi. You can get these by temporarily change the ‘jessie’ entries in /etc/apt/sources.list to ‘stretch’, run apt update and install the required packages manually. Change back to ‘jessie’ when you’re done.
Be aware that Stretch is still unstable though – and that there’s no telling that DietPi will continue to behave nicely after installing them. Also: NAA only releases its grip on ALSA when the HQP application is fully closed – you won’t be able to stream to Roon Bridge while HQP is running.