Fun fact: Studies show it's hard to shoot people with three broken bones while being buried five inches deep in some old drywall. That and there's brick dust literally everywhere. I'm not even sure if Vae is still inside, or if she's even in one piece. Also, the building is coming down. Might wanna find a way out.
I wouldn't wanna get onto the rooftop, in case it collapses before the ship arrives, but it'd probably the the safest place if you want to survive that horde coming in. The question is, what's going to happen first? Will the ship arrive, then the building collapses, blocking off the horde? Or will the horde arrive and the ship lands, only to be crushed by the building? Who knooooooows? Decisions, decisions.