A few red flags to look for are as follows. See if the contractor has WCB, GST number, Insurance, Business license, safety program in place, and ask how their relationship is with their supplier. These are very important because you want a professional roofing company to do your job. Try not to hire a company that says they will do it for cash under the table to save you the GST. Those are the guys that will do the job and if you have any problems with it down the road, they’ll disappear and you’ll be left with extra costs of fixing their mistakes. During the selling process if you have difficulties getting ahold of them, or they never seem to answer your questions. These things should be red flags, because how a contractor acts through the selling process thats how they will treat you during the installation process. Check out the company for yourself, ask around. If no-one has heard of them before then maybe there is a reason for that.