The simplest is actually to add "role" claims in the token issued by ACS. Since you said you are ok in doing this manually for now, then you'd use the ACS portal to create these rules.
In your app, you'd do the usual thing, like decorate the actions with the "Authorize" attribute, including roles:
[Authorize(Roles="Administrator")]
public ActionResult Index()
{
var b = User.IsInRole("Manager");
...
}
As long as you use "Role" claim types, everything works. (This can also be customized, but it works out of the box this way).
The only challenge you will have is due to LiveID. LiveID gives you just a unique identifier. You need a way of mapping that identifier with a know user (e.g. e-mail or name). This usually requires a two step process. You first authenticate and get the unique id, then you ask the user for its information and validate it (by sending an e-mail for example).
Using any of the other identity providers, you don't have this problem, because all of them give you an e-mail and a name.
Writing the above mentioned rules is as easy as:
- email: joy@mail.com -> role:administrator
- email: someone@mail.com -> role: manager
...
If you have a larger number of users or a larger number of rules then the portal is often no longer practical and you will need something else (e.g. use the API from your app, use scripting, use a tool like auth10, etc.)