The airline will let you "drop" the 1st sector as long as you get it repriced and reticketed, but you cannot expect to get the ex EWR fare when starting in PHL
If you misconnect on the 1st sector , the airline will be obligated to get you to Rome on another service.
For USD2550 ex New York, there are other options such as going via LHR on BA rather than backtracking to PHL which will allow you an easier connection , as well as being able to check baggage through from PHL to FCO
If you are happy to get from LGA/EWR to JFK , can get the non stop service from JFK-FCO at $2505 on the outbound
Last edited by Dave Noble; Jul 5, 2015 at 1:22 am