Unfortunately Ruckus has somewhat bowed out of the broadband gateway / NAT router business since the MediaFlex units. I'll let Ruckus speak to their future plans / intentions, but right now you can configure standalone APs to do NAT and act as a gateway using one of their WAN ports, but that configuration gives you very basic control over DHCP, NAT forwarding, and introspection into WAN-LAN traffic. It is also challenging to selectively firewall the WAN interface to not expose any curious Ruckus services (like SSH, HTTP/HTTPS, and the couple of Ruckus management related ports) while not losing those functions on the LAN side.
Bottom line, right now, I personally recommend investing in an inexpensive NAT gateway device and letting Ruckus do what they do best: delivering the best possible wifi on your LAN side. This situation might change in the future, but quite honestly, most NAT routers are quite good even at low price points.