I decided to steer clear of Rocks after learning that setting up this private network is fairly easy, especially in Linux.
I used Fedora 20 and an unmanaged 5-port ethernet switch. I connected all nodes to this switch, via ethernet of course, and went to the WiFi settings, which is the network settings window in Fedora.
Here I went to the wired connection and changed the IPv4 IP address and Subnet to 1.1.1.x and 255.255.255.0, respectively. x here is a counter which is incremented for each node in the cluster, so I have address 220.127.116.11, 18.104.22.168, etc. Of course if you're making your own cluster any address will do, for most intents and purposes.
This is most of the work. However, I was having trouble connecting to this private network. I found this is because it was trying to do things with the IPv6 address information. So i turned this off and the computer connected right away.
From here I wrote some "Hello World" OpenMPI programs and ran them. This required a machine/host file and credential-free SSH connections, but these are issues for other threads.