I wish I could give more than 5 stars!
The apartment is nicer and bigger than the pictures would make it seem. The living room is large enough for me to have my private salsa lessons (and Karla is nice enough to let me have them). The bed is extremely comfortable. The desk and chair are comfortable to work from and the WiFi is great. There's a huge wall-mounted TV with Netflix, and even an Xbox 360 (never used it, but still pretty cool).
The location is perfect, and extremely safe. It's a 5-minute walk from lots of nice restaurants and street food, and is centrally located to access lots of other great spots in the city.
Karla is an amazing host and flatmate! (and her incredibly cute dog, Picolina, too). She picks me up and takes me to the airport, is responsive, always friendly, and helps me whenever she can. She even made a bunch of calls to help me find a doctor appointment on short notice.
I don't think you'll be able to find a better place in Roma :)