Depending on the state laws, it *might* be something he/she could have fixed but it also would have to be really close to the selling time, not 'years later'. It would depend on the disclosure laws of the state, and the code specs for roofs.
I'd say find out first what state the OP is in before worrying about the 3 layers. Most of the USA is not actually in heavy snow-line country . That seems to be the main area where 3 layers and weight is an issue.