How can I make a security module using SharePoint ?

Question

We have developed a great system using WSS 3.0 that contains about 450 lists in one site, in one site collection. These 450 lists are for 53 modules in which each module has some lists.

We would like to make a security module for this system in which the administrator can make roles with access to some lists with certain permissions and assign users to this role.

NOTE: We use WSS 3.0 SP2 and can upgrade to MOSS 2007 if necessary.