Although most new homes are covered with asphalt shingles the life of your roof can last as long as 15 years, but the most common reason homeowners call correcting a leak is a seam break. If you live in a new home before the roof was finished allow 2-3 years for the warranty and the existing roofing should be inspected by a professional roofing company to determine if a likelihood of water penetration is possible due to weather or possible roof repairs on your existing home.
If a seam flaw is found there are three areas to look for. First, look along a wall straight from the ground as far as the leak is possible across the seam. If no bubble is visible it means the roofing company performed the job correctly. The second area to look for is the missing or curled roll of asphalt shingles. A EM region (a large area similar to the name recognition area, to show where a EM is to be located, typically icons or shapes near the downspout on a roof) is the outside area that connects to the right deduct of the otherwise equal area on the ground. Check the area of the EM with a level. If it is almost vertical then that is the area of a potential vulnerability.
Blown-in asphalt shingles are tricky and costly to repair so much so that most professionals use felt paper or other temporary repairs to cover over the area. However, once the leak has been located you can begin the process of stopping the leak.
The most common asphalt roof is a lay-on felt grit system designed to fall under the weight of the surrounding shingles. When the gutter is inspected next walk around the gutters edge and look into the gutters. Be sure to wet your shoes. If you can feel a gap in the gutter, there is a pipe inside your wall that is leaking.
Once you have located the source of the leak it is time to patch it. First use a good quality clear tar caulk to seal the seam using a spacer (it can also be caulking around a window). Next, use a good quality spray roofing underlayment to cover the seam under the tear in the gutter. Use a blow torch to apply the seal and then keep applying more seal until the leaks are covered. Let it dry for 1-2 days and then your ready for brand new beautiful asphalt shingles like the ones you purchased. You may want to repair the leaks you may get a second opinion from a reputable roofing contractor.
If you have any question about your ability to repair and repair damage to roofing material, definitely call a professional roofing contractor. The work could be dangerous to even talk about and if your home is an older structure but a homeowner you may be subsidizing the full amount that you would have to pay for the work to repair your roof.