ssh to root

[Aryeh M. Friedman]

I need to set up a machine so that I can type "ssh [host]" as root from 
some other host and I get a prompt with super user privs... I already 
have set this up for user at host for root and ssh host for normal users... 
but root still asks for a password after I set the authorized_keys file 
in ~root/.ssh.. I have looked at ssh_config(5) but can't tell what 
option (if any) does this... if anyone is coruious the final goal here is to set up a sysutils/fusefs-ssh for this host (already installed and working for normal users but want to make it so it is done as root)