Find out what users haven't been assigned roles?

I'm trying to find out what the sql statement for finding out what users haven't been assigned a role.
I know that I have a user that I have basically turned off access to the two roles that I have set up.
My code so far:
SELECT aspnet_Membership.Email as eMail, aspnet_Roles.RoleName FROM aspnet_Membership CROSS JOIN aspnet_Roles where aspnet_Roles.RoleName = 'Admin' or aspnet_Roles.RoleName = 'Member'
What's the best way of finding out from all the users that I have available within my application i.e assigned roles?
 
I hope I'm making myself clear?
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