An idea I had, inspired a bit by this topic.
Removable rooftops
Basically, I put together the tiles from the tileset to make the roof I want, then I use an event to place it there. Afterward, I make an outline, like the box/ceiling from the inside tileset, and set it up as the inside roof. When that's done, I place code into the doors to change the roof event to the inner roof image and back again when leaving using switches. In the third screen you can see the event that holds the roof images being highlighted in the outside field. The event needs to be centered at the bottom of the roof to line it up right.
Using this small event system, you can make inside and outside rooftops for up to eight buildings per characterset. I plan on using this in a game I am making.