If you haven't got it yet, I thought the plot was utter nonsense that seemed to have had scenarios imagined up and then threaded together with the barest or logic (or none in many cases).
After a couple of rolls you will have as much of a story as this film and indeed may have produced a more interesting one. Now simply roll the two dice and make notes of the combinations - Custer's rifle, the President's watch, the Queen's bedroom etc etc. However to summarise National Treasure 2 it is probably easiest just to take two dice and for one die assign each number the name of a person in history (Queen Victoria, Nixon, Custer), then for the other assign an object (a table, the Empire State Building, a book). Normally I would write a plot summary before I review a film - it helps introduce the film in case anyone is reading but mostly I do it because it helps me focus my mind on what I have just seen.