I run FreeNAS with RoonServer within a VirtualBox. The FreeNAS Server (9.10) runs on an AMD Fusion E-350 with 16Gig of RAM. It’s a dual core 1.6Ghz CPU. It runs more than fine with up to three RoonBridges attached over a wired network.
One of them is a Raspbery PiI 3 with a Hybrid Tube Amp bought in the Kickstarter.