keddy by Europcar
Booking in advance not only ensures a better chance of getting your vehicle of choice, it can save you up to 91% on your car hire. For a below average price at Roma Airport, Cheapflights recommends booking your car hire at least 6 days in advance.
Typically, how long you can rent a car for depends on the inventory of the supplier. For Roma Airport however, it is certainly possible to rent a car for an entire month.