Over 200,000 dollars later in remedial renovations to our home, I would advise knowing your roof very, very thoroughly before looking for a roofing contractor. If you have other than a simple gable, make sure you understand its every twist and turn, where it jogs out, what ventilation is needed. Get a couple of home inspectors with established reputations and/or a structural engineer to help you assess the issues.
Then - make your roofer show you each step, put it in writing and sign it, photograph it - whatever. Mine lied and then stonewalled when we had leaks into kitchen - blamed it on the gutters - and when all was said and done - our gutting and repitching project showed all their shortcuts and angles left out.
Fix any water problems within 48 hours and remove all wet materials - else you could end up with unhealthy mold which insurance could blacklist you for.
Scary - you bet. Worth the research trouble - unless you're loaded, absolutely. Understand your building envelope!