itch.io

Go out the man door, go to your right, along the wall. Easiest way to discover it, is to have the help box (for me it's F1). You'll see where it says in the box to open the gate. Press the key that you use to open the gate and the roof will disappear.

Yeah eqicfailninja is correct, if you walk outside the door and immediately turn right and walk down the wall, youll see the trigger