Outdoor Christmas decorations are designed to be waterproof and safe to use outside. Buy decorations that have cords that are rated for outdoor use and use protective boxes or wrapping for added safety. Indoor decorations should never be used outdoors since their electronics are not weather-resistant.
Take care when placing decorations on the roof. Read manufacturer instructions carefully, as some wireframes may be too heavy for safe rooftop use. Never place anything near a chimney or vent. Inflatables should never be set on rooftops, as they can get caught in the wind and blow away.