It sounds to me like you need to implement your own ASP.net Membership Provider, or at least extend an existing one:
http://msdn.microsoft.com/en-us/library/f1kyba5e.aspx[
^]
If your requirement is to redirect to a different url depending on Role, I'd try overriding the
ValidateUser
method of the provider, call
base.ValidateUser
inside your override and add any custom redirection logic after the call to the base class.