Rome has so much to offers visitors so three to four days will only allow you to get a glimpse of what this great city has to offer. However, if you plan your visit wisely you will be able to do and see a lot in those three days.
Many of the main tourist attractions are relatively close by so you can walk or take taxi or buses. Hop-on Hop-off buses are also a nice way to get an overview of any city. There are plenty of great places to eat in Rome, catering for all tastes and budget. I am attaching few links that should help you to plan what to see and where to eat during your stay in Rome.
Hope you enjoy your visit to this great city, try to stay four days if you can. over 9 years ago