I would go through the usual cliches that I've seen everyone posting about their hosts, but I don't have the time.
This was my first AirBnB experience and even though I can't compare it to a past experience I know that if I go to Rome again soon, I'll be staying at Rosa's.
Do not hesitate to ask her anything you need. Definitely one of the most genuinely helpful people I have ever met. Room: clean, bright, fresh, perfect air-conditioning. I'm a smoker, so the balcony was a wonderful advantage. Per Rosa's recommendation I tasted sweets from Pasticcheria Siciliana nearby - exceptional Gelato, and if you're a fan of pistachio, your mind will be blown. I discovered bar oasis the day I got there - lovely people, great sandwiches.
Final word: when in Rome, avoid the tourist packed museums. Attend the INCREDIBLY well curated Museo Nazionale di Arte Moderna.