I built a nice bungalow on top of Red Rocket with some beds for settlers but no one seems to use them even if I remove the beds on ground level. I have it very close and I can run up the stairs without having to jump or anything. Is there just no pathing for NPCs to follow? I tried to order Dogmeat up there but he won't go either. Am I just wasting my time on second story stuff? Thanks in advance.

They do use stairs, make sure there is nothing obstructing the stairs, NPC need more room to move around then you do. Tight corners should best be avoided, there seems also to be a problem if stars are too close to doors.

http://i154.photobucket.com/albums/s240/Axe_Gaijin/2015-11-22_00020.jpg

Hmm.... I wonder if I have to put flooring on top of the Red Rocket roof itself. Maybe the game won't recognize it till I actually build something. I have lots of room around the stairs.

I built a huge 4 story tower megaplex on top of the Red Rocket. You just need to make sure you

A. Have completely smooth stairs up and down directions. Use the little stair step piece or whatever placement to make pathing not get blocked

B. Not technically necessary but having two or even theee separate stairs/access points up and down make pathing a lot easier. Sometimes two npcs want to go up or down, and despite not even being on the stair to block each other. It seems the game goes into a loop of 'after you maam...oh no, after you good sir...no really i insist, ladies first...'

They get stuck without being stuck and when i build two ramps up it became ton better, and with three i never had issue again.

Your stairs have to connect both upper and lower surface. If your stairs hang just little bit in the air at the either end, AI will not be able to use them, no matter that you can. I always test my stairs by ordering my companions through them. If they are unable to do so, I try to reposition the stairs.