Each user needs to have an account on the nix machine.
They also need to have samba accounts (using the smbpasswd command).
Roaming profiles are actually fairly easy.
Do it a step at a time. Once you are able to log on then work on the roaming profiles.
I highly recommend checking out:
and read up on the Learn Samba : By Example section. Very helpful.
I'd give you more but my machine is away right now.