My family will be in Rome this December and would like to travel to another city or country. We will have only five days in which to travel; where should we go
Need more info do you have five days total (for Rome and another country), or five days in addition to Rome? It really depends upon what interests you. Travel within Europe is pretty easy and whether by train or plane, you can get to just about anyplace in Europe in five days and enjoy it. One approach would be to look at the various airline web sites and see if they are running specials to certain cities from Rome. If you see a combination of an attractive place to visit and a good price, then that might answer your question. However, given that it will be December, you also have to factor in weather. Even Sicily and Malta get fairly cool in the winter, but Spain will have some warm locations if you are interesting in going someplace warm. I mean, the sky's the limit, from a quick ski trip the Alps to a few quiet days in Paris, to any other number of cities. You could stay in Italy that whole time and just do day trips from Rome or do a mult-segment Italy trip. So if you want to provide more info perhaps we can offer some more specific recommendations. Otherwise, know that it is very easy to travel within Europe and relatively inexpensive also.
Do you already have your airline tickets? If you have round trip tickets to Rome I would stick to Italy. You could go to Florence or somewhere else that would allow you to easily get back to Rome. If you have not purchased your tickets you should consider flying open jaw, also known as multi-city. You could fly from Rome to Paris, and home from Paris. The weather will be cold, so take that into consideration when deciding a destination. Indoor activities are good. That is why I suggested Paris. There are plenty of indoor things to do.
I'd think one direction out of Rome for a brief excursion. In five days I'd probably visit Florence with an intermediate stop in Orvieto but you can pick a direction out of Rome and pick some stops.