The problem with tin roofs is condensation in the winter. Consider Ondura or Polycarbonate.
I shingled my roof and my run. I'm pretty sure they'll outlast me.
The coop is well constructed.
The attached run is too small though. I'd increase the size to at least 150 sq ft.
I'd lengthen the rafters to increase overhang and leave the soffits open and backed by hardware cloth, install a ridge vent and the largest gable vents on each end that you can. Also...