A one-year old house with a leaky roof is not good news. And the builder's claim that it just the soffit getting wet is pure BS. As Hatchet has noted, water coming in will end up in walls and places where it shouldn't be, causing no end of grief. You need to figure out where the leaks are happening, and why. Best way is to get into the attic (assuming you have one) and see if you can trace where the water's coming in. The usual problem spots are valleys, end-walls, chimneys and the like if the flashings have not been properly done. If the leaks are happening at the eaves (assuming you don't have ice dams) then I would suspect really shoddy installation. Do you have a new-home warranty? You need to document what you observe, and perhaps have a professional roofer or qualified home inspector give you second opinion.