Ok, the fist thing you do is shoot out the window at the side of the building near to the ghost, shatter the window to the right as you walk up the mud path. Next crouch and walk into the left hand side of the frame, there should be a large shard of glass just above your head and this will prevent you from standing up when you let go of the crouch button.

Let go of the crouch button and you should stay crouch, walk straight forward into the frame and make sure that your ridicule is just on the left side of the glass shard. Your screen should start to shake, when this happens, making sure that your ridicule is just to the left side of the glass and your holing forwards, JUMP and keep holding forward.

When you hit the ground you should bounce way up onto the roof.