Assuming that you are asking whether a single RRAS server can handle routing between two LANs, yes, it is. But you don't need it if you are doing simple routing.
If you enable "IP Forwarding" on an NT4 Server with two NIC's you can route between 2 LAN's. There are improvements to the routing engine and a lot more capabilities in RRAS, but RRAS adds some complexity that some admin's would rather do without. I typically use RRAS when setting up dial-in/dial-out modem banks and VPNs.
If this isn't what you were asking, try and be clearer.
ShackDaddy