Currently, the cheapest month to rent a car at Roma Airport is June. The most expensive time to rent a car is March. The cheapest prices for each month are shown above, but prices will vary based on availability, how far out you book your rental car, and of course, car type.
From Avis you can hire a car at Roma Airport from about $803 per week on average.
Typically, how long you can hire 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.