CAESAR II won't design a rod support for you. You pick a node that you think needs a vertical support and simply specify a "Y" support. Now, if the results indicate that there is significant upward load, or significant horizontal movement, then you the Engineer must decide if a YROD would be a better support model at this location.

Once your satisfied with the performance of the system, and you have the forces and moments at the supports, then you can design the support details.