Is there a way to place an object, say 8 ticks up in the air, and then proceed to place more of the same object at 8 ticks in the air without dragging it up from the ground? i.e. it stays hovering while you place it multiple times. It's such a pain in the lime to make roofs.

Yeah, if you build a roof piece at 8 clicks in the air you can then just hold down control after placing the first piece. Once you hit control the piece should be at 8 clicks. When I do this it does not get the height right the first time, but just keep trying.

And you will also find that CTRL works fine on one side of your project but not on another, or it might work in the middle three tiles but not in the end ones. Keep an eye out or you'll be deleting as much as you place.