roof or drylining walls first
Well, does your roof leak now? If it leaks and they put in new drywall, and it rains, the new drywall could get leaked on &amp; possibly ruined.

Even if the roof doesn't leak now, they have to tear off the old roof to put a new one on, and they really should wait for good dry weather to do that but sometimes they don't, or unexpected storms appear. So without a roof you almost certainly will have leaks inside the house, again possibly ruining new drywall.

So, with good weather it shouldn't matter. But if it rains &amp; leaks, it will matter. Why not do the roof first?