BAS helos can do a fast rope onto a roof. If you do not want to program it yourself, use my "GP Helo Script" in the editors depot (click "Latest Submissions"). I just checked it on Novoga, and it works fine on a rooftop. You my have to fine-tune the placement of the "H" object on the rooftop, but the script gets it much closer than trying to do it with waypoints.
The only issue is the $%# BAS scripts set the behavior to RED of the troops as soon as they hit the ground, so sometimes they will run OFF the rooftop! Best workaround is a trigger that sets then back to YELLOW (stay in formation) as soon as they leave the helo. Then they won't break their legs running off the rooftops!
EDIT: I meant the BAS scripts set the **combat mode** mode to red, not the behaviour. Sorry. Setting the combat mode back to yellow fixes it.