In our recent Magic Tracking Tutorial, we used a new preset to help locate a specific point on a surface tracked with Mocha AE. This technique works well to establish objects onto a specific location like a sign but you can also slide objects on the surface as well. This example shows the ability to animate that point along the surface by keyframing the position of the NULL.
For the boulder I used CC Sphere with some fast rotation and manually scaled the ball as it reaches the camera. You can even download the project and see how I did the other effects as well but I encourage you to check the Magic Tracking tutorial to see how it works. There is no 3D tracking and it was all created within After Effects and tracked with Mocha.