After a quick look at the nfs booting code, I have fixed my root mount
problem.

The summary for the dhcp.conf is:
-- The bootfile specified in filename is tftp-ed from the next-server
   (which defaults to the DHCP server machine)

-- When the kernel has booted and nfs mounts its root filesystem then
   if the (option) swap-server is set it is used as the nfs server
   otherwise the next-server is used.

Mark