Hi Steve, have you looked at tripadvisor. They have a lot of B&Bs listed for Rome that members have been to. I have put the link for it below. Take a look. Not been there myself but have used the site for other hotels in different countries and have found it to be helpful.
Thanks for the link. Yes, I know TripAdvisor and have used it a lot. In fact, we have now settled on this one (not cheap but all the comments seem very positive):