Do I have a roof leak or something else?

I have wet spots on the drywall ceiling and it is starting to crack slightly which have become stained when they dry in my upstairs daughters bedroom. The spots are just before where the ceiling meets the wall. I am wondering if this is definitely a roof leak or is it something else because the wall/ceiling in question is opposite the bathroom shower. Is it possible the shower could be leaking through the ceiling/wall or would it definitely be a roof leak. My roof is about 15 years old and we have had some hard rain recently but I just am not sure that it is a roof leak. My attic is very small and I don't think I can get up there.