Yes, Terminal 5 is only for departing passengers.
From the airport website:
Terminal 5 has been built for departing passengers of American Airlines, Continental Airlines, Delta, United Airlines and US Airways and has been designed with the aim to increase the capacity of Fiumicino airport intercontinental area. In the past years overcrowding at Terminal C has caused quite many problems to passengers. The new building is just at a short distance from the airport terminals, it extends over a total surface area of approximately 14,000 sqm and it is subdivided into three main areas: an area dedicated to profiling activities, a check-in area and a security/passport control area that also includes the gates to the shuttle bus service, which transports passengers to the West Satellite for boarding operations, covering a short-distance journey of 800 m only. The security check area also provides a Fast Track service for frequent flyers and business class passengers. Services available to passengers are a pharmacy selling OTC products, a coffee shop, soft drink vending machines, a baby-changing unit and a special assistance lounge available to disabled passengers located in the profiling area.
For a map of the airport and more details
click here.