One downside to rolling it then placing it on the trailer is the gunnel height. In my opinion, with a boat this size and type, completing the hull and sitting it upright puts you about 15% done with the project. There is still a lot of work to be done and most of it will be inside or on the base hull. You are going to be making hundreds if not thousands of trips from the floor up over the hull side and then down to the deck or hull bottom. There were days I know I easily made 30 or 40 climbs up there. On the trailer your lowest access point will be over 6' off the ground with the trailer being about 2' of that. My point is the lower the boat is to the ground the easier it will be to work on. Mine was sitting about 2" off the floor but required 5 steps and still had to step over the side. The photo below will give you an idea of the height. It can certainly be done on the trailer (the one in the above photo was completed that way) but for me lower is better.
One other suggestion is when you get to this point build a good solid stairway to access the boat. Don't even think about a ladder. Disassembling the building form will supply more than enough 2x6s and carriage bolts to build it. You can see mine along side the hull. In fact, until I started to finish the hull exterior it was screwed to the boat for stability. I had several shop visitors mention the need for a handrail and for safety they might have be partly correct. But my feeling was it would very often be in the way when I handled larger pieces while getting in and out.
After completion I still use the steps. They are now in the storage shed and I use then to get into the boat. They still are situated beside the boat but now because it is on the trailer the top landing is level with the swim platform. Works out well. Oh, and yea, I did add a handrail.
