Roon decodes the files itself and then sends a decoded stream to the endpoint, so the Aurender would be essentially a NAS if RoonServer were running externally.
An important design goal of ours is that all content that Roon supports can be played on all devices, and that that support works retroactively, even with older devices that haven’t been updated–as soon as we start trusting devices to handle the raw source material (files or protected streams from providers like TIDAL), it becomes impossible to support that level of interoperability.
Something happens very couple of years–a new streaming service comes out. We’ve done some kind of integration and relationship with at least 10 (probably more, but I made a list in my head, and I count 10) such services the eight years that I’ve been in this space.
TIDAL is pretty new–about a year old. Hardware older than about a year old can’t handle TIDAL streams directly. But Roon can play TIDAL to older hardware because we handle the stream and then convert it into a form that the device can understand.
The same is true of DSD and high-rate PCM when playing to AirPlay or Meridian devices. In almost any category, there are devices that can’t play all of the content.
There is also a quality argument for minimizing the work done on endpoint hardware, and offloading as much heavy lifting as possible to a server running in a different box, on a different power supply from any analog audio circuitry.
The point is: Roon processes the audio internally, and then sends streams to endpoints in a fashion that requires as little additional processing in the endpoint as possible. This is a core idea in our architecture, and is unlikely to change too much.