If you find good resources written by Roma themselves, I'd be very interested in that! I am so, so wary of books about groups of people written by outsiders (at least as a means of learning about the people, rather than learning what outsiders think of the people). Though you do sometimes run into the issue that what the dominant culture considers history or ethnography does not even make sense through the people group's own cultural lens, so it's hard to develop any real understanding without talking past each other.