Limitng root access

I've been working with FreeBSD and recently with Trustix Secure Linux; in both systems I've found a nice feature: the only users who're allowed to su root are the mebers of the root group. I haven't found how to do this in SuSE (currently working with SuSE 6.3 and 6.4, and switching to SuSE 7.0 soon), is this possible? Thanks in advance, Andres Tarallo