I'm a long time truck camper, and am now considering adding a fifth wheel to the mix. I was thinking toy hauler, but only because my wife and I each have bicycles. I know a toy hauler might be overk...
We use one of two options: The best one is when it is just my wife and I, I simply put the bikes in the back seat of the truck with the seats folded up of course. This is by far the best way as it keeps them out of the elements and from theft. Once in awhile when we have others with us then we use our 4 place bike rack on the rear of the fifth wheel as it has a 2" receiver.