Oh no, now I have to confess that I use duct tape. Yes, it is nothing more than strips of duct tape stuck to a sheet of corrugated cardboard. In fact, it's black duct tape so I don't even paint it -- except to add a wee bit of character. The roof took me about 5 minutes to make.
I picked out this duct tape specifically for this purpose and tried to find a type that had a nice texture.
Look for Gaffer's Tape, from any theatrical supply house.
Not as cheap as duck tape, but dead flat & unreflective.
Gaffer's Tape has a surface texture very much like electrician's friction tape, but wide.
I can imagine it would do a splendid job of portraying a tar n'gravel roof.
Which I have several to construct from DUST bits n'bric-a-brac...
Thank you for the wonderful tip sez he heading for his theatre toolbag...
Valerik
50 years a notorious Thespian