I don't mark roofs on inspections for real estate transactions. I try not to leave any sign that I was there at all since the deal may fall through and I hate it when the seller calls to complain because I dropped attic insulation in the hallway, didn't put a box back in the same exact location in the garage, or what-not.

That being said, when I do a newly built home inspection or end-of builder warranty inspection, I will use chalk on the roof to identify the nails, etc as the house is either already owned by the client or the chance of them backing out on a new home is pretty slim, plus, even if they back out, the builder usually doesn't mind if I mark spots for his punch list (providing the punch list for the builder is a whole other topic ). I mark these roofs on the new homes because I was tired of doing follow up inspections and finding none of the nails sealed etc, even with good photos and descriptions of locations. But, for that matter, on many follow up inspections on the new or 1 year old houses, I usually find that many of the repair items were never completed, even though the builder said they were and even had a color photo guide (my report) to find the issues.

That's my take,

Eric