AD-authentication with custom roles in SQL-DB

[Sale]

I am writing an asp 2.0 website where existing AD users can log in.
I am using ActiveDirectoryMembershipProvider for this task and it
works.

Now I need to define roles for these users (admin, author, user...)
These roles are not defined as groups in AD (in fact there could be
other web-applications with a different set of roles and users), so I
am looking into creating a separate database where these roles are
stored and mapped to the AD-users.

From my understanding, the Membership and Roles are managed by the

same database Visual Studio 2005 creates. But in my case I have
Memberships defined in AD and Roles should be in SQL-DB.

Is this possible? Am I missing something basic? How could I map roles
to users?
I am using IIS, so I have no access to the ASP.Net Configuration Tool
to set up roles.

Thanks for any hints!

Reinhard