I don't know about SuSE, but with mandrake, using kde as the default window manager, they opted to not give root graphical login access by default.
To cure that (well with mandrake/kde), you just open the kde control panel, then go to system>login manager.
You'd then have to hit the "administrator mode" button at the bottom of the screen and input your root password when prompted.
You'd then just click on the users tab at the top and uncheck the box for "hidden users".
After that, when you next log in you would have root showing an option for graphical login.
As I say, that's how i'd do it in mandrake, with SuSE it might point you in the right direction!
hope that help's some
p.s. or you can do like linmix says and open a terminal and type "su" at the $ prompt and them put in your root password