Nobody can answer your question since you left out most relevant facts.
Generally speaking, a worker is an invitee so that as the homeowner you have the duty to make necessary inspections of the premises to make sure there are no hidden defects to cause his injury. However, if he is injured outside the scope of his work, for example, using a restroom without permission, then he is a trespasser and you only owe him an ordinary duty of care that you did not cause his injury negligently.
If he is injured durnig his work, such as falling off the roof, unless you closely supervised his job, you have no liability.
You should contact an attorney and provide details for further evaluation.
