I definitely recommend Roberto's place. The apartment is amazingly well located - very close to the Vatican/St Peter's in a good area with plenty of options for food and drink; steps from Ottaviano metro, so it's easy to get downtown; convenient for getting to and from the airport. It was much bigger than I expected: the apartment has lovely high ceilings, a big bathroom, and a separate bedroom with plenty of closet space. The kitchen and front room are vast, and it's all well-equipped. Roberto is a great host with lots of tips: he gave me some good advice on using a bus to get from the airport to the apartment. Moreover, when there was a problem with water pressure in the building, he contacted me to let me know he was looking into it even before I'd realized it myself (as I was out at the time); he left some bottles of water to tide me over, and resolved the problem before I got back to the apartment for the evening. A great experience overall!