I would just stay out of it if I were you. Without first hand evidence, it's more likely than not that you'd just stir up unnecessary, unwarrented, trouble by acting on what you've heard from the secondhand, possibly unreliable, source. Besides, even if the employees of the roofing company you hire do say something crude to someone else, that isn't your fault, and the person actually spoken to is likely more than capable of taking whatever actions, if any, he or she feels that are necessary regarding calling police, complaining to the management of the company, etc.
Of course, if you hear something first hand, or if something is directed at you, that would be a different story and you would want to act in whatever way you found appropriate. But based on the "information" you have now, I honestly think there is no good you could do by acting on it, and if anything, only possible harm.
ETA: Congrats on the new roof!