So you only want to access services FROM the roadwarriors withing your existing network and not TO your roadwarriors.
I Think you can just enable advanced outbound NAT and NAT from the roadwarrior-subnet to your existing network.
For servers in your existing network it would seem as if the connections come from the IP of the pfSense-machine:
http://forum.pfsense.org/index.php/topic,7001.0.html