Nytzsi, if you hear roaring all the time and the exhaust is too hot to touch all the time I think you should shut down the gas supply. Something is very wrong if it never stops firing and this could become a safety issue. If you call a plumber try the yellow pages for your area and call a licensed plumber. Like any industry there may be a crook or two out there but most plumbers value their reputation and word of mouth referrals.