C# - Overriding SQLMembershipProvider / Adding Few Extra Methods To Deal With The Roles By Using LINQ?

Is there built in methods into .net framework to do the following:

Get role GUID from user name/user GUID
Get role name from role GUID

So far I have been sending queries to the asp_roles and asp_users tables to obtain that information and I'm wondering if there is a nicer way of doing this?

I have the following methods that I store in the ASPUtilities class:

getRoleGUID(guid userGuid) { LINQ joins }

getRoleGuid(string userName) { LINQ joins }

getRoleName(guid roleGuid) { LINQ joins }

EDIT:

I have just looked into extending SQLMembershipProvider examples.

Few examples completely override the SQLMembershipProvider, but I think what I'm interested is just adding few extra methods to deal with the roles by using LINQ. Is this feasible?