How to access Membership/roles through silverlight

I have a silverlight control on my asp.net mvc page, need to communicate with a webservice where i need to send the current role of the user logged into the system w开发者_StackOverflow社区ith. But how do I access the "Roles.GetRolesForUser()" from within my silverlight application?

http://blogs.msdn.com/brada/archive/2008/05/03/accessing-the-asp-net-authentication-profile-and-role-service-in-silverlight.aspx

I hope that helps you out.