DAP ALEX PLUS Acrylic Latex Caulk Plus Silicone outside is what I used on the wall to wheel well joints and other places on the sides, back, front to refresh caulk joints as needed. I caulked then immediately put the wheel well trim back on. The back side of the trim is pretty close to the wheel well in a few places and some caulk will ooze out so be ready with some rags or paper towels to wipe that off before it sets.
Unless you were assured it was just done the joints between the roof and the front cap and rear top trim need to be maintained at least yearly to keep them water tight, so you may need to make sure yours were maintaned this spring before you bought the Edge. You can't use regular caulk for this joint this needs to be a product made specially for trailers with membrane roofs called Dicor Self-Leveling Lap Sealant, the kind you need for an Edge with Rubber Roof is a light green tube with the part # 501LSW. If its good you will see it tight against the membrane and the cap / rear trim and no gaps that water can enter. There is also a special seam tape compatible with the roof membrane that can be used to seal these front and rear lap joints that is more expensive then just using the Dicor lap sealant. It costs more to do it that way but it may last longer so that you are not buying another tube of Dicor every year.
One final thing - it is very thin and relatively soft material that the trim screws are screwing in to on the Edge - you are best not using any power tools to run the screw back in - even doing it by hand you can't apply too much force or the trim screws will strip.