Repairs on a roof can be from many different causes
When you are aware of a leak, you need to find a solution quickly. When the rain comes in, everything has a chance to get damaged. You need to have a professional find the source of the leak and repair it correctly.
If your roof is new and you are having a problem of leaking, the first thing to do is call your original roofer or contractor. They know what has been done so they should be able to find the problem quickly and repair it. If you can not find the roofing company you used or they won’t return their call, then find someone else as soon as you can.
Any moisture coming in can turn into a much larger problem. If previous workmanship has been shoddy or unprofessionally completed, you could have leaks soon after it has been done. The problem needs to be determined and the work completed soon. In some cases, a newly roofed area needs to be reworked to fix the leak which can be costly.
If your roof is closer to 15 years old, then you probably are looking at getting a new roof. When a lesser quality shingle was used, its life expectancy is much shorter than the better and best quality shingles. Some brands have had recalls because of shoddy production and if your shingles are curling or falling off too soon this might be the case. Find out the brand of the shingle on your home if you can.
When a better quality shingle was used on your roof it will probably be about 18 to 25 years before you are replacing them. Look for curling, cracking, loose granules in the gutters or loss of the shingles. If you have a leak with older shingles repairing is just putting off the inevitable and you will be spending more money than just replacing the whole roof. The shingles can no longer do their job of protecting your home.