-- SQL 2005+
exec sp_addrolemember @rolename = 'myRole', @membername = 'aUser';
exec sp_droprolemember @rolename = 'myRole', @membername = 'aUser';
-- SQL 2008+
ALTER ROLE [myRole] ADD MEMBER [aUser];
ALTER ROLE [myRole] DROP MEMBER [aUser];
Note: role members can be any database-level pri...