By default Rocks does not configure your second ethernet card (most likely called em2). You can easily verify this by issuing rocks list host interface compute-0-0. You will see the missing details for the second ethernet card.

To configure this, you need to run the following for each compute node.

rocks set host interface ip compute-0-0 iface=em2 ip=10.1.2.40
rocks set host interface name compute-0-0 iface=em2 name=kodospublic-0-0
rocks set host interface subnet compute-0-0 em2 public
rocks add host route compute-0-0 0.0.0.0 10.1.2.1 netmask=0.0.0.0
rocks sync config
rocks sync host network compute-0-0

The 10.1.2.1 is the gateway to the outside world. kodospublic-0-0 is just a name for the interface. The public ip (10.1.2.40) is the network ip for the compute node (must be a different one for each).