Theres a lot of old buildings in Boston, most of which do not have roof anchors, In the past , it would have been find what you could to tie to and just do it
These days where safety higher on the agenda, what do you do, within the rules
OSHA says that you must have 2 independant ties offs for each drop , capable of supporting a load of 5000lbs,(i.e. just because it looks like it would is not good enough, it needs to be certified by someone with the credentials to do so) and within 15 degrees of perpendicular of the drop
A roof rig is not good enough as that itself has to be tied back
