has he met and greeted your neighbors when they aren't in the tub?
perhaps, with a treat given to them, to give to him, if he sits like a gentleman, and obeys your commands, will lighten the barking. he may be barking at the unknown.
the roof- well it is noisy and different to see people on a roof so i would walk by, show him, and reassure him (soft voice, nice doggy no barking, no one there) kind of stuff.
he's really not reacting so out of whack. more protective than anything else. regardless of the vibe. i wouldn't want to hear a noisy dog at that hour either, and i have 3 dogs.