I have no roof since I ran out of my 200 concrete and after building multiple tier II machines in order to build more, it takes 40 minutes to make basically an arm's span worth of more concrete, so to fill my roof would take hours and hours of gathering and waiting. Combine that with the fact that once you do place down your roof it disappears once you exit Build Mode. So, no roof since I don't have the patience to deal with this insanity.