Looks strange but it is only on one panel of wood. Wouldn't mold be spreading across the boards?
It looks to me like weathered OSB roofing in the second picture. The first picture is likely concrete/mortar. Construction companies will generally still use boards that were used for mixing or forming concrete/mortar. If it were mold, it probably wouldn't be isolated to those single boards and would be "creeping" over the roof trusses. So in short, no, it's not mold.