Roof is signed with your two flat hands forming a roof in front of your body. You start with your flat hands together at an angle, all fingers touching each other and palms facing down. Then move both hands apart and at a downward slant simultaneously, creating a wide-angled inverted 'V', just like a roof.
It is similar to the sign for house, but you stop short of signing the walls. You only sign the roof itself.
Roof is best taught to your baby or toddler when you are actually demonstrating the roof of your house or of any other building when you step out for errands or a walk.
Teach your baby the roof sign in conjunction with live oculars in the neighborhood or city, or at home with your home-related flash cards.