To clarify some confusion on Private Zones:
Zones are composed of 1 or more endpoints (multi-endpoint zones are what we called grouped zones, so you can play the same thing in two locations or more). We only support grouped (or some people called it “linked zones”) with kind types… so for example, Meridian zones can link to Meridian zones, and Airplay with Airplay. USB zones can not be currently linked, but it is on our roadmap.
A Roon Remote exposes its own outputs as zones, but the idea is that Remotes are transient in nature, and not fixed infrastructure. For that reason, we chose to call them Private Zones and make them only accessible from the remote itself. They may not be the feature you are looking for, but they are the right feature for some scenarios.
For the situation where you want to use computers, tablets, phones, network audio components, etc as your zones, and those devices don’t support Airplay, Meridian Streaming, or SongCast (in dev now), then you need those devices to run RoonSpeakers, which is our own streaming protocol that solves many of the issues related to latency, buffering, clock ownership, clock drift, samplerate/frequency negotiation, etc. It also allows us to build user experiences like we do, unlike pull based protocols like OpenHome and UPnP (we really need to write that blog post I’ve been promising about why the pull model leads to bad UX).
Anyway, we are working with 20+ hardware partners at the moment (more being added daily post-Newport) to add RoonSpeakers to their devices. Many of the brands you love are on our list. On top of that, we are going to be releasing RoonSpeakers as a Mac OS X application that lives in your menubar, a Windows application that lives in your system tray, and iOS and Android apps as well. We even have something working on the Raspberry Pi. I think you guys have already convinced us that a Linux build (headless) needs to be released for Roon and for RoonSpeakers.
So, where private zones won’t meet your needs, you should run a less transient endpoint that isn’t tied to the Roon application, software RoonSpeakers!