I'm running RoadRunner as follows:
New base station connected to the cable modem.
iMac w/ airport card downstairs
Wallstreet w/ airport card in another room
iBook w/ airport card roving throughout the house.

No problems.

My understanding of RR is that they will authorize and service use for a single computer. In the event you wirelessly "attach" other computers, they will only be responsible for problems you have with the "authorized" computer. RR does not prohibit one from adding additional computers and there is no extra charge for so doing.

You will set base station per instructions and tcp/ip to airport and DHCP

Hope this helps/E