It is up to you, the homeowner, to do your due diligence in a little detective work before hiring people to work on your home. You need to protect yourself from being liable for the injury of others who you hire to work on your house.
First and foremost, you should be sure the contractor is licensed and has insurance. Don't just glance at the paperwork, follow through to be sure everything is UP TO DATE. An expired insurance policy or one that is behind in premium payments is worthless in the event of any personal injury. Also, insurance is provided in the event that the contractor makes a mistake or does something to damage your property. Say he did not properly cover your landscaping and the torn off roof pieces breaks your shrubs to smithereens.....you want those shrubs replaced, right?
So, do check any licenses and insurance policies....at their source. You should not be responsible to pay insurance for someone elses business practice.