How do I configure my router under another to avoid NAT issues?

I'm sorry if this has been answered before; I tried looking but couldn't find a solution. I'll try and explain as clearly as I can.

I've recently purchased a Rogers Mobile Rocket Hub and it's causing issues with FTP connectivity. Here is our network layout:

• Rocket Hub (gives 192.168.1.1 as LAN IP)

  • Buffalo Wireless Router (192.168.1.2, gives 192.168.0.1 as LAN IP)

    • Comp 1 (192.168.0.3 --- this device has FTP)
    • Comp 2 (192.168.0.4)
    • Comp 3 (192.168.0.5)
    • Etc. etc.

  • Rocket Hub LAN port 2 connects to Buffalo Router WAN port

Normally I would prefer to set the Rocket Hub in bridge mode but that isn't possible. That would not be so much of a problem except that it also cannot assign IP addresses based on MAC addresses...which is what I currently have the Buffalo router doing.

What is the best way to avoid problems with this setup?

------- EDIT -------

OK, so thanks to your help things are working now! Here's the new setup:

• Rocket Hub

  DHCP turned off
  LAN IP = 192.168.0.254
  Port forwarding rules set
  LAN port connected to LAN port of Buffalo Router

• Buffalo Router

  DHCP turned on (serving addresses from .2 > .221)
  WAN IP determined automatically
  LAN IP = 192.168.0.1
  Port forwarding rules not set as they aren't needed (don't know why that is...)

• Devices

  Hooked up to Buffalo Router...gateway, ip all automatically determined via DHCP

Disable DHCP on the RocketHub.
Set the internal IP of the Buffalo to like 192.168.0.2 (or the .2 of whatever subnet the Rockethub uses by default). Set the default route of the Buffalo to point at the internal address of the Rockethub.
Plug the LAN port of the Rockethub into a LAN port of the Buffalo.

That will let the Buffalo still provide DHCP, but all traffic will route through the Rockethub. No more Double-NAT.