I sometimes find evidence of rodents in roof spaces, particularly in rural areas near open countryside.
The evidence is usually in the form of droppings, sometimes nibbled pipe foam insulation and on occasion, more dangerously, electrical cables.
The most humane way to (try) and control these pests is to lay bait which can be legally purchased from your local hardware store. Take great care with it, and top it up from time to time. Much less messy than the traditional mouse trap!