I have cradles in the front as well and rollers at the back. I too have removable cradles that fit on top of the rollers at the back. I fit these before I start driving. So my boat rests on 4 cradles. Many aussies prefer to not have the hulls be touched by the trailer and suspend the boat on its beams. I finally decided to go with the cradle option and my hulls are surviving very well indeed. I have a timber hulled F16. Spread the load out well and you'll be fine.

The rollers make it very easy for a singlehanded sailor to load and unload the boat (singlehandedly)

Wouter