StarterSTS uses the standard ASP.NET membership, roles and profile provider. The easiest way to connect StarterSTS to other data stores would be to use custom providers that can work with these data stores.
Below you'll find more information what kind of functionality a custom provider would need to provide.
StarterSTS uses the ValidateUser method to authenticate users and the FindUsersByName method to search for users.
StarterSTS uses the GetRolesForUser method to find roles for a user.
StarterSTS itself uses the profile provider in read only mode.