If I am a renter of a townhome and the roof is cleaned regularly by some guy with a blower, who is liable if he gets hurt?

Who is responsible for roof maintenance? If it is the HOA as well (presumably, since the HOA is hiring him), and the HOA also hires him, then if he is injured on the job, it should be the HOA that is potentially liable, not you, and not the townhome's owner--not unless one of you did something that caused the injury in some fashion, in which case you might be liable due to that action. (E.g. if you were, say, washing a windor or watering your lawn while he was up on your roof, and you somehow negligently splashed him, startling him and causing him to fall, that could make you liable.) From what  you write, any contractual relationship, any supervisory relationship--indeed, any relationship whatsoever--would appear to be with the HOA, not the owner and certainly not a renter. Therefore, the only basis for imposing liabilty against you would seem to be  f  you caused or contributed to injury, through a negligent or intentional act.