ASP.Net Membership provider without using database

Hi,

I am working on a website that needs authentication/authorization, one thing special about this site, it does not store user/roles, instead it relies on other sites to authenticate users and redirect browse sessions to this site with user/roles embedded in http headers. I have questions:

1) I guess I have to implement ASP.Net membership and role providers in this case. Is it worth the effort?

2) The site does not have a log-in page since it does not do authentication. How will membership provider be invoked?

I am kind of new to this so I actually  prefer to roll out my own but my manager and colleagues prefer to use ASP.Net membership providers.

Thanks