You may never find out if the trusses needs to be repaired unless it was pointed out to you by a home inspector if he/she really inspects the house or your roof looks bowed from outside and you have noticed it by yourself.
When providing an estimate for a customer, not too often but there are many times that I notice the sagging that was caused by broken roof truss. It becomes a conflict for me because it is not safe for me or my staff to be working on a roof that has possibility of caving in. Right away i document the problem with pictures from different angles to show it to the customer. Once the customer is aware of the problem i must inspect the attic visually and determine the exact cause and location of the problem.
It is a serious issue that may be caused by the heavy wet snow that was parked on the roof every winter, poor workmanship or bad material. It all depends on the size and shape of the house. The way it was constructed has a big part on how and why. Roof trussesare engineered and you
To prevent similar problems in the future, remove wet snow off your roof, have your roof inspected by a professional roofing company, when buying or selling a home hire a local roofing contractor to inspect the roof and the attic.