The tilex is going to dry out a lot faster than the wood will. That's
because the tilex is just on the surface of the wood, whereas the
moisture in the wood has had the time to penetrate into the wood cells,
and it takes a lot longer for water to evaporate through the wood cells
walls than it does for Tilex to evaporate directly into the air.
That just looks like wet wood to me as well.
Really, what you need to do is scratch at that wet wood with your finger
nail. If you can scratch that wood away with a fingernail, it's rotted.
Otherwise, it's fine. Wood, being a natural material, stands up to
occasional wetting much better than most building materials (like
plaster or drywall).
I wouldn't bother with Tilex. I'd spray bleach straight out of the jug
on that wood to kill any mildew or mold that might be there.
You can avoid further wetting of that wood by providing for an air gap
between the insulation and the roofing boards, and allowing cold outside
air to get in at the eves of your house, and out through a ridge vent
along the ridge of the roof. The idea here is that the unavoidable heat
loss through your insulation drive a convective air current from the
eves to the ridge vent. That convective air current dries out any frost
or condensation that forms on the underside of the roof.
The other side of the argument would be: If the house is 50 years old
(I'm thinking because they used lumber for the roof sheathing instead of
plywood or OSB), and there's no wood rot, then why not put the existing
fiberglass insulation back in, and we're good for another 50 years.
And, I would have difficulty giving a good reason NOT to do that.
Millions of houses across North America don't have any roof ventilation
at all, and yet most of them never have any serious problems with wood
rotting in their roofs.