get root on a remote Host

[Lado]

Hi!
Ich use emacs 22. I use Tramp over ssh to edit my files on remote Hosts
very often. From time to time i need to get root on a remote host. There
is no Problem to get root on the localhost with /su::, but i was not
able to find any solution how to get root on a localhost.
P.S.
i can not login as root on a remote host, because ssh root login are not
permitted.

Thank you!