Roof questions.Will a leak show inside before its too late?

i guess the main place im worried about is on the side of the roof... right above where the drip plate is... where does the rubber go, does it attach underneath that? i noticed a couple small holes on my new camper along that long seam right above the drip rail.. im not sure if this is sealant that has little blemishes in it, or if thats the rubber roof itself... i might just plug it up anyways with dicor to be safe..wont hurt..