Structurally your options include putting the roof panels just over a framing system.
How to cover circle roof with metal panels.
This is part 1 of a 6 part video series explaining how i installed a metal roof on my house.
If there are gutters installed on the eaves the eave flashing should be installed to overhang the lip of the gutter by about 1 2 inch.
You do have some options in metal though.
If you are installing over an existing surface mark the studs with a pencil before installing panels.
Place corner pieces where panels will meet bends at the edge of the roofing.
In this video i cover measuring the roof figuring the metal th.
To make a truly round roof in metal you need eitehr tapered panels or some of the metal panels will work.
This video shows a unique and ez way to mark and cut out an electrical box hole in metal siding.
Whether installing metal panels on walls ceilings or as a roof the process is the same.
If you segment the roof into a bunch of pie shapes though you can use other panels as well.
My main tool for perfection.
Install metal panels with ease.