Safety when working on a roof
Work at height is among the riskiest activities on a site, which is why it's regulated by health and safety at work rules (Law 319/2006). A serious team uses harnesses, lifelines and scaffolding where needed.
As the client, it's in your interest that the people climbing onto your house are insured and properly equipped. It's a sign of professionalism and it also protects you from liability in case of an accident.