Initially, I was not happy with the idea of saddle/gator rolls because I saw it as collapsing the ruck but I have been convinced over the last season or two that it is a good way to expose the ball. For me collapsing the ruck means dragging the ruck players down on top of the ball/other players in such a way that it kills the ball and/or endangers players on the ground who have been unable to roll away.
I don't see any problems with it so long as it meets those last two criteria, i.e. that it is done by rolling the player away from the ruck/tackle, and not in a manner that endangers other players or the player being rolled away. However, for this last reason, I am still not convinced that saddle/gator rolls should be allowed at junior levels where there can be a huge disparity in strength between players.