What is drip edge?
A major component of a decent roof is drip edge. Drip edge is a 2 inch by either 2 or 4 inch piece of metal that goes along all of the edges of your roof. It goes under the drip edge on the peaks, and over the drip edge at the gutter line. The main purpose of it is to prevent water from curling under the shingle and down the fascia.
Throughout most of Colorado drip edge is required by building code. It definitely should be, although you find that in a lot of other states it is not required at all. Where I grew up in Alabama for instance, instead of using drip edge contractors overlap the shingles at the gutter line and bend them down to create a kind of waterfall into the gutter.
The drip edge that we prefer to use is 2 inches by 4 inches around the whole perimeter of the roof. The standard practice is to use 2 x 2 inches on the peaks and 2 x 4 inches in the gutter. Although slightly more expensive, when you put 2 x 4 around the peaks too, you are increasing that metals protection by 2 more inches which adds a lot more value to the project than the money you would save using 2 x 2.
**** Sidenote: If you are having your roof replaced, ask the contractor to paint the drip edge on the peaks to match the fascia if the color is not close. It looks much, much better this way.