How many roles are in that club?
select count ( position )  from member_of_club where clubid  =   ( SELECT T2.clubid from club as T1 join member_of_club as T2 on T1.clubid  =  T2.clubid group by T2.clubid order by count ( * )  desc limit 1 ) 
roles in that club refers to count of distinct positions in the most populated club;