As most people are aware, the recent hail storm has brought out a flood of "contractors" who are going door to door trying to solicit your business. They ring your doorbell and ask if they can go inspect your roof and look for damage. They might assure you that "insurance will pay for it". One such contractor came to my house and started off by saying he was in the neighborhood replacing a roof on a nearby home. Yet when asked, he couldn't give me the name of the neighbor or the location of the project. 

If you need someone to inspect your roof, consider finding a reputable, registered and insured contractor. BBB ratings and Yelp reviews might be useful. You can obtain a list of registered contractors from the County's website (use the first available link, but beware it's slow).  Also refer to Chapter 24 Article 1 of the DuPage County Code for regulations applicable to solicitors, which includes info about how to post "No Soliciting" signs.