My wife and I spent 4 nights at Rosa's apartment and loved every minute.
It is in a great location that is pretty much central to all the main sights and close to great restaurants.
The unit itself was great - clean, light and best of all at this time of year - cool(air conditioned).
One downside was we found the bed a bit too hard for our liking but other than that Rosa's apartment was perfect. Sad to be moving on actually.
I highly recommend to anyone looking for an apartment in Rome to consider Rosa's.