I have no idea why anyone would elect to use some roofer who calls out of the blue! There are many reputable companies available that you can research should you need that service. I would simply NOT use anyone who calls unsolicited. Roofer, car warranty (!), pest control, etc. Why don't hairdressers call randomly??? Or doctors????
I have received from 1 to 5 calls every day from 1/24/17 to today(1/31/17) despite having been blocked after the first one. They are using an autodialer as they receive a recorded message that I am not receiving calls from their number. Any human with half of a brain would know calling was a waste of their time.