It will affect any OSX that is new enough to have that code in it. Same is true with other OS. For instance, on an older, patched FreeBSD 7.2 system, we see this result:

  /root/.ssh/config: line 1: Bad configuration option: UseRoaming
  /root/.ssh/config: terminating, 1 bad configuration option

... which means that sshd predates the roaming code. I haven't tested, but I'll bet my snow leopard workstation also predates that code.

So ... if that line:

  UseRoaming no

produces no errors when you ssh as that user, then you had the problem and you fixed it. If it produces the error above, you never had the problem in the first place (although with an older sshd like that, you should make sure you're not exposed to other, older vulnerabilities).