Honeymoon - last dinner in Rome!
There is an endless stream of queries on this board very similar to yours if you search for special dinner or anniversary dinner in Rome you will find some.
Second, If you have an idea of whats most important, cost, traditional or inventive food, ambience proximity to your hotel, etc. pls supplement your request. You will get better recommendations.
Here is one long thread on the topic http://chowhound.chow.com/topics/804094
Our family of foodies searced out moderately priced restaurants for our 8 day visit. Of the places we visited I'd suggest LaPiazetta, not far from the Coleseum, I believe it's in the Monti neighborhoodd. Fabulous antipasta bar, and great food and service and atmosphere and value.