If you are going to give the GC serious consideration, you will need to do some digging. What kind of reputation does he have? Any references from previous roofing jobs? Who will actually do the work and what is their background? You are entitled to ask these questions. Notice how he answers. Does he talk fast, and then change the subject after two sentences? If so it may be a red flag. Does he seem honest,down to earth and attentive when he talks? Aside from hearing him talk, and deciding what make of him, pause. What kind of feeling is this guy giving you? Do you feel (not think)that you'll be in good hands? Or do you get a sense that there is something you are unable to know about him--another potential red flag. These are subtle things that may be useful when weighing a decision. Trying sense a person in this way may not be for everyone, but this approach has been very helpful for me.