Get All Roles, But A Select Few / Get All The Roles Except Administrator?

I have run into a problem where I need to remove certain items from collections that seem to only have get all functions.

My Idea is to get the full collection and then remove the unneeded items. Then take that new collection and bind it to whatever I need.

For example How do I get all the roles except administrator?

Roles strRoles = Roles.GetAllRoles()
RoleList.DataSource = (Roles) roles; //Roles.GetAllRoles();
RoleList.DataBind();

or How do I get all users but say user123

MembershipUserCollection users = Membership.GetAllUsers();
UserList.DataSource = users;
UserList.DataBind();