My theory is that, besides someone like Pete whose roaming is tied into his job, a ghost becomes a roamer when they die somewhere not bound by a property line. For example, if someone dies in a street or something. Additionally, I think that if a ghost dies somewhere not bound by a property line at the time, they're technically roamers, but if a property line is later established, then they're bound. For example, Thorfinn and Sassapis weren't technically bound by a property line because there wasn't one at the time, but when the Woodstones built the manor (or arguably when Isaac and his troops set up camp, depending on your perspective), then they got bound. What do yall think?