tar paper or a much better choice rubber impermable membrane is a
essential part of the keep dry system.

blowing rain can get under the shingles and cause a leak. this happened
to my travel agent her home builders kids crew didnt remember the tar
paper, after numerous roof leaks and insurance dis owning the water
damage it finally got fixed had to replace roof.

other things to do when replacing roof, REPLACE flashing everywhere,
covers around serer vents, how about ridge vent upgrade, drip edge and
inspect all chimneys and chimney caps for cracking which can cause CO2
poisioning and death... lighter color roofs last longer and help keep
home cooler in summer, dark colors absorb heat.