Multi- Registration possible?

Hi

For a project we have been looking @ various options, and Drupal won with what we needed.

I want to know though, as I can't seem to figure this out. I have created 4 roles, as follows:

nonymous user locked
authenticated user locked
event organizer edit
exhibitor edit
service providers edit
site admin edit

Now, is it possible to have a different signup form for each role type? The reason? Each role type will have different abilities and different functions. How would I do that?

I understand the roles and the access rules, to some extend. How would I configure my Drupal so that the different role's users can each do their own thing.
For instance:

I want the "service providers" to be able to list their services, and each one have a contact form (with some pre-set defaults). The exhibitors on the other hand should be able to create pages & stories, but only within their allowed menu (I have a menu in the primary links called exhibitions), and the event organizors should be able to create menu's, add stories & pages, and also allow users from either the exhibitors group, or the service providers group to have access to create stories & pages.

Does this make sense enough?