Get datacenter or resource pool by using vRO script

I'm currently building a service blueprint but don't want the user to have to enter resource pool or folder information.

How do I retrieve objects such as a datacenter or resource pool using the vRO scripting language?

I'm currently trying to use var myDatacenters = VcPlugin.getAllDatacenters(); to retrieve a list of datacenters to search through but I am returning zero results.

Are there any tricks to doing this?  Do I need to connect to vCenter first?  Is vCenter perhaps not communicating with vRO?

Any help would be greatly appreciated!