When you watch videos online of champions rolling, they execute a lot of the basic moves as well as advanced moves with ease. But there are very subtle differences between them and an average athlete that may be hard to pick up.
A few noticeable differences:
1) Their selection of moves
2) The set ups for these particular moves
3) The number of steps involved in each move
As the sport of BJJ evolves, so do the moves and more and more of the top players begin to add the same moves to their repertoire. This is not by accident, and should be noted.
Watch this following video by one of the best lightweights Augusto Tanquinho Mendes and see the high level of detail in it.