Good question. I have read only one article about the incident, and it did not say how they managed to get up on the roof. News reports on the local SF news radio station also failed to mention how they got up there. However, I do know from going past the Consulate that the Chi-Coms seem to occupy the entire building, so I don't think they could have gotten up there via another tenant's facilities, or anything like that. Time will tell what really happened.
First, she fell only fell about 10-15 feet onto a balcony and broke her arm on a flagpole on the balcony. I think they got to the roof from an adjoining building. The guy from the consulate said that you protect yourself when someone breaks into your home.
They interviewed another protester, They looked to be 17-18 year old naive American girls (spoke perfect English).