Get the city inspector out, I know it will mean pulling a late permit
but it should only be 20$. Say the roofer forgot to do it. Then ask for
an inspection . This is city inspectors job, is free-you actualy paid
for it, and is why everyone can benefit from pulling a permit. If you
found 2 things wrong he may find 20 more. Document everything in
writing, as in emails. and record conversations, I do on contracts.
Photograph issues before they fix them. Get a sample of paper from the
roof to confirm it is 15lb, Email the manufacturer to see what they say
about 15lbs adverse life spam vs 30. Then ask for a rebate of what you
think is fair. If they refuse or are jerks, file small claim, its easy
and cheap 35$ for me. Even suponea the inspector if you must go to
court. I have done this. You should check his insurance and lisence, he
is a hack and you never know what you will find. Your issue is common.