Logical World - Cut down on sources of moisture, increase ventilation, when the roof is replaced assess the plywood for damage and replace as needed.

World we live in with blood sucking attorneys trying take food off our table - Same first two + further evaluation from a mold remediation specialist. Super extreme cases the mold guys will call for total removal, mid-range they'll call for sanding, minor they'll just call for bleach washing.

There was an instance I was involved in that defied all logic... House was about 15 years old. The 3-tab roof was totally shot and needed to be replaced. The soffit vents had been completely cut-off since day 1 and the bath fans had fallen many years before and were venting 6 people's showers worth of steam into the attic each day.

Now, any logical person would just tear off the roof, re-deck the roof, hook-up the bath fans, unblock the soffit vents and live happily ever after, right? Nope, the mold people scared this poor guy into sinking 6K into remediation which included sanding, triple bagging and properly disposing of the shavings. The entire roof and decking could have been done for less than that. Problem is nobody (myself, real estate agents, sellers, etc) is going to tell someone to go against what the mold people say. So, now the guy is left with a 15 year old roof with ultra thin sheathing and an empty wallet.

It's like when someone asks me about lead paint or asbestos.... do they really expect me to tell them not to worry about it. I can just hear it now as I'm sitting on the stand.... "Let me get this straight, you told my clients not to worry about the lead paint that eventually poisened their 4 children?"

Sorry to be so longwinded... I hope somewhere in there I helped out with your question.