The announcement of a peaked roof lets members assigned to roof position know that they will not be going to the roof and will perform other duties. If its a flat roof, the position can be made and ventilation (skylights and scuttlecovers) can be opened. For safety, our procedures dictate venting a peaked roof from a TL bucket or aerial. You wont see guys climbing along a ridge or using a hook ladder. The size hole you can make for the risk is not worth the a effort. I saw one peaked roof opened in 23 yrs on FDNY, I did spend my whole career in the Bronx though where tenements and H-types were the norm