"I'm staying," he replied quickly. It might not be an ideal place to be, but he simply wasn't comfortable leaving Iris in her present condition - whatever that may be - around people so traumatized. Chances were that people on the roof were going to act erratically and irrationally, and Micah already had too much on his plate.
It would be much easier for him to just go in and stay out of the way. If he happened to see how the man who lived up here had spied on Iris, that would simply be a bonus.