Black spots in attic

[Ataul Munim]

I'm looking to buy a new house. Had the inspection yesterday. Inspector pointed out black stains in the attic. Is this mold? New roof was installed in 2008, but the sheath appears to be original. Should I be concerned? How big of a problem is this? Thanks.

[Raymond Wand]

Very well could be mould, but without testing to confirm its only a guess.

Appears to be localized and would need to investigate further as to cause.

i.e. roof leak, damaged vapour barrier, exhaust fan from bathroom not vented properly, poor ventilation of attic.

[ROBERT YOUNG]

I suspect the attic/roof deck venting is compromised.

[John Kogel]

That amount of staining on old OSB is pretty minor. I won't say there is no problem, but from those two pics alone, I'd say there was a roof leak at the ridge, probably now dry since the roof was replaced.
That second pic, some water stains, cause unknown, maybe condensation. Still pretty minor, as your inspector should have told you.

[Ataul Munim]

Thanks everyone for your opinion. Quite helpful!