You should be able to find and repair the leak yourself. This is particularly true with a newer one like yours, where the primary materials should still be in good condition. Once you repair the leak, it would be wise to inspect the roof at least twice each year to find problem areas before they leak.
You will have to use an extension ladder to climb up on the roof to inspect and repair it. Remember these safety tips for ladders. Before climbing the ladder, extend it out on the ground. Put your weight on each of the rungs to make sure it is sound. Even if a rung does not totally break, just a loose one can make you lose your balance. Always have a helper supporting the ladder.
Whenever climbing on a ladder to get on a roof with nothing to grip up there for stability, the ladder should extend four rungs above the edge of the roof. Make sure there is a suitable, level base for the ladder. The ladder should be tilted at an angle of about one-quarter of its height from the base of the wall.
A short “flat roof 101” lecture will help you to understand and better analyze where the leak may be located and why it started to leak so soon. The typical flat asphalt roll roof consists of several layers with roof cement in between the layers. The final layer is then covered with gravel or small stones to protect it and to block the sun’s damaging ultraviolet rays from reaching the top layer.
The location of the dripping water is seldom directly under the location of the actual roof leak, but still, check there first. You might get lucky and find the leaking spot immediately. The common spots for roof leaks are around the flashing and where the roofing has separated from roof vents or the chimney.
Also, look for any exposed nailheads that have come up through the roofing. Check where the water typically flows into the gutters. These areas will be easy to spot when you are on the roof. Look for areas where the gravel covering is missing or shallow and where the roofing asphalt laps at seams.
If you find nailheads, don’t worry about driving them back down. Clean the gravel off from around the nailhead. Using a putty knife, spread a heavy coating of roofing cement over and around the nail. Push the gravel back over the repaired spot.
If you find a tear, use a scraper to remove the gravel. Cut a piece of roofing larger than the tear. Spread a layer of cement over the tear and press the repair piece over it. Spread another layer of cement over the repair piece and lightly press the gravel into it.