Well, I haven't done much in Linux, but I can offer the following general words of advice:
If your RoadRunner service is anything like mine (AT&T nee MediaOne) they probably use straight-up DHCP to lease you an IP based on your MAC (hardware Ethernet) address. So, if you install the DHCP client on your box and get it running, it should get an IP no-problem.
That said, I was never able to get DHCP working on my old SuSE 6.1, but I'm lame with Linux, so YMMV.

One thing to consider: if you have tons of problems with your distribution and (even better) if you want to hook multiple systems up, buy a hardware router like the Linksys or Netgear and let it do the DHCP work, then give your Linux box a static IP via the router (assuming your router supports it) and let the router handle it with NAT.
Again, this is by no means the true Linux way to do things.
-- Kevin