animation/physics help

Hi, I m am trying to develop a game on android, i was stuck on this particular part. I am confused with how to go about creating something similar to this:

Crash Bandicoot 2 - Crash Dash - YouTube (from 14seconds onwards).

i want the object to be rolling downhill and for the object to only drop once the character cross’s a certain part of the game to follow behind the character. Would i need to create a live animation? if so, i have never done that before so some help in the right direction would be great!

No live animation necessary, if you have rigid body on, check use gravity (should be default checked), and just have the boulder roll down the hill and have a gap wide enough for the boulder to drop off. Leave the rest to level design.