Cut the roof out and paste it onto the story you want to see it on. You will have to elevate it all down to the correct height (you can do this before you okay the paste or afterwards). You will also need to redo any Solid Element Operations if you have performed any with those roofs.
That's how ArchiCAD stories work - you place information on the stories you want them to appear on them. Their actual elevation is a separate issue.
Hope that helps.
Cheers,
Link.
