The advantage & disadvantage of the rollers is how easily the boat rolls on them. This doesn't help you decide what the best trailer to get is, but I always get a kick out of this when it gets brought up.
Quick story... While bringing my boat in to the ramp, I was waiting on the water for another boater to launch his apparently recently purchased bass boat (from a roller trailer). He backed it down in the water, started the motor and couldn't seem to get the boat off the trailer. He had his partner back him further down into the launch, still couldn't move. Now the trailer is well sunk and the boat should be floating. Buddy backs in even further. At this point, the transom is heading under the water rather than floating and everyone on our boat can deduce the problem... owner obviously didn't unstrap the back of the boat. With much frantic yelling and screaming, the boat driver gets the truck driver to pull him back out of the water.
Now safely back on the dry ramp, boat driver hops out and goes to the rear of the boat to see what the problem is (bear in mind, he's taken on a fair amount of water). Upon walking around the rear of the boat, he immediately sees that he didn't take off the outdrive support. He reaches over and unhooks a quick release from the outdrive. The boat driver notes that his beautiful boat is rolling backward off the trailer toward him! So, as any good boat owner would do, he plants his feet on the sloped launch and begins pushing on the back of the boat while yelling and screaming for his buddy (who is casually walking to the back of the boat to see what's going on). Boat owner is putting up a fight, but is getting pushed down the ramp as the boat is slowly rolling backward.
Truck driver now sees what's happening and decides to help push rather than go up front and rehook the winch. There's a short discussion between the two of them at the back of the boat (while struggling mightily to hold the boat) before one of them makes a dash for the front and gets the winch hooked back on the boat.
Nothing I could do but watch as I'm 75' off the ramp waiting in my boat and my truck driver is on the other side of the parking lot retrieving our trailer.
I had visions of this beautiful boat sitting on the concrete boat ramp, but they actually saved it. Seemed like it was sitting 1/3 of the way off the trailer. I was almost certain it was within inches of the tipping point.
I'm not normally a fan of laughing at other peoples woe's, but no boats were damaged in the making of this memory, so I have no problem laughing about this ego squashing moment