There are a variety of ways to apply Shingles to a dollhouse roof, but the fastest I've seen is to use a hot glue gun.
1. Mark your placement line directly on the roof with a straight edge and a pencil
2. Have your shingles ready to work quickly with
3. Have the hot glue gun ready and a safe place for it to rest
4. Apply a thin line of hot glue directly on to the pencil line. Quickly place your shingles on the line. If the glue at the end of the line is dry - re apply and apply a shorter line on the next application of glue.
5. Draw another pencil line where you want to place the second row of shingles and repeat #4 until your project is finished.
Be careful not to burn yourself. Any aging, or staining you want to apply to the roof can be done now. The roof can be protected with 1 or 2 coats of a matt varnish sealer- Use acrylic so it does not yellow or smell.
Enjoy your Shingling Project!!!