u/Individual-Tune-3013

So after you beat Rhodagn in Abberant Zone 6, you can enter a room which leads to the roof of the building. Notice this is the "throne" or stage where Rhodagn stands between the phases and there is a switch you can use to activate the flamethrowers for which I assume is to force him back to the fighting ground.

I tried this now only to discover that during the boss fight this roof area and the room behind the fight area is closed off, making the use of this mechanic impossible. Is there something I'm missing here?

Thanks in advance.

EDIT: Thank you all for the explanation!