Timing of Roma (B)/Catan (B) and Courtesan's Guild?
On boardgamegeek.com, Jacek Deimer says he has asked Antoine Bauza (the game author):


  If Courtesan Guild is built in the same turn that ROMA/CATAN recruits extra leader, can it copy leader recruited during the same turn?


Antoine answered:


  No


So Alice has to choose a leader card to copy (guild card effect) before Bob recruits his leader (wonder effect).