User Registration

I was wondering if there was a way to set up user groups with permissions and as people register on an intranet site, the fields they select will then place them into a user role. So for example if they register and choose one of our business units and fill in their address they would then be put into the business unit group and the state group they are from.

I need to control permissions on a page level and show and hide certain pages depending on certain user roles.

thanks in advance.

AP.