Postgres inherit from one role and not another
I solved this by nesting the two roles together. 

    CREATE role elevated_role nologin noinherit;

    GRANT ALL PRIVILEGES ON ALL tables IN SCHEMA db to elevated_role;
    GRANT usage ON SCHEMA db to elevated_role;

    CREATE role normal_role nologin noinherit;
    GRANT usage ON SCHEMA db to normal_role;
    GRANT select on ALL tables in SCHEMA db to normal_role;

    GRANT elevated_role TO normal_role;

    CREATE new_user with password 'some_pass';
    GRANT normal_role TO new_user;


This allows me to manage the users in a group by just adding and deleting them from the group but gives them separate roles that they have to explicitly set if they want to insert, delete, etc.