It is a pre setup fanless Intel NUC based computer. It runs their Roon OS which is a modified Linux and is locked down so nothing else can run on it. The Nucleus also has the extension for Control 4 integration. A plug and play setup.
Alternatively, you can get your own Intel NUC, download the ROON OS image, also known as ROCK, and put it together / set it up yourself. Good for those like to DIY and/or those who want to save money.
Also, alternatively, you could use any Mac or Windows PC and load Roon or RoonServer on it.
A really good starting place is to understand the Roon architecture: https://kb.roonlabs.com/Architecture
Like Scott, I am a fellow helpful user. Roon does not have a direct sales number to call as far as I know; I believe their sales are handled by dealers or via sites like Amazon.