SpeleoFool
100+ Head-Fier
So, first and foremost, Roon is a music library manager. It also manages streaming on a local network. It seamlessly integrates Tidal (also Qobuz) and, IMO, provides a better overall interface for navigating your music collection than the native Tidal interface.
One killer feature of Roon (for me) is that it is exceptionally good at supporting music exploration--everything is hyperlinked, so you can dig into credits, follow individuals or contributing artists and go listen to their material. On a whim, I even looked at album credits and clicked on the photographer for the cover art--and found 6 or 7 more albums in my collection with him on credits!
Another killer feature is the ability to support multiple streams and, with limitations, link streams together. With some planning, you can use Roon for whole-house music. You can also transfer tunes between endpoints, which is nice when I need to quiet things down--I can transfer a song from my 2-channel setup to a headphone setup and keep the music going.
That's just a sample of features Roon offers. In the context of A&K players (or other DAPs), the advantage of Roon support would be (when on your home network) to send a digital stream over WiFi to your DAP and use its DAC / sound signature, etc., to listen. Your DAP would no longer be bound by what's on its internal storage, and you could use a tablet + Roon interface to more easily browse music and send it to your DAP. It's mostly a matter of improved convenience, but once you've played with Roon and discovered all the fun ways it lets you interact with your music, you'll understand why having Roon support on a DAP is so appealing.
Roon, generally speaking, doesn't do anything magic to improve sound quality. Rather, it's good at preserving sound quality. The Roon architecture uses a central server (Roon Core) that manages your library metadata and directs all of the streaming over your local network. One or more computers or devices on your network act as Roon Endpoints and receive the audio streams. The Core knows about the capabilities of each endpoint and will optimize the stream to each endpoint to send the best signal quality it supports. Roon also handles MQA unfolding. Generally speaking, if you have a quality endpoint that supports a wide range of formats, then Roon will send your track to the endpoint in its native format--you get the exact native bits of the track, unperturbed by transcoding or DSP. If you have a DAC that doesn't support MQA in hardware, Roon can handle the unfolding in software and send a full-quality PCM stream to your DAC.
I skirted the topic of add-ons like HQPlayer, but if you wish to have Roon upsample your streams before sending them out over your network you can do so. Personally, I prefer native format over upsampling, but I've read plenty of positive reviews from people about HQPlayer. If you're into tinkering, knock yourself out.
Since A&K players have such wide support for high-res formats, Roon's ability to preserve native formats or upsample is a good match for A&K's ability to play them back. FWIW, Roon accomplishes this by using their own custom digital transport protocol called RAAT. Older formats, like DLNA, are bandwidth-limited in the same way as OG Bluetooth or S/PDIF (optical/coax). RAAT was built from the ground up to ensure that all of your bits get from the Core to the Endpoint without needing to downsample the audio stream. I suspect RAAT support is (was?) the major hangup behind the waiting game with A&K's Roon support (although there's also a certification process, so no telling what i's need to be dotted and t's crossed to get the final, official signoff).
