I had shingles installed just last year and roof is already leaking

You should definitely call the roofer, it sound not be leaking, however it may not be attributed to his work if a. The materials are defective or failed. B. The water is not coming from a pipe or something else that may run through the ceiling/roof. Or C, act of nature where he had done all work correctly and strong winds or unusual driving rains have caused it, but you should definitely call him regardless so he can look and to fix it if it is his work that was substandard, thing is you may not know as he is supposed to be the expert, all you can do initially is hope he is honest and will rectify it, of it is down to him or help you if it is one of the other reasons

Get the roofer back out to look at it.

Hi, firstly what pitch does the roof sit at, is it a mono pitch or single pitch, did your expert install proper welted drips around the perimeter including the hip details if any, and how is the crown flashing installed? External Photos would hopefully be a advantage. Call your expert and ask to rectify .

First answer is good should get hold of the roofer it could be the head laps are wrong or the roof pitch is low so you should reduce the gauge of the shingles