Happy Bob and I were able to inspire this masterpiece.
I had a lot of fun deciphering which way to roll and when.
Some ingenious moves and misdirection in this city.
I start at the bottom, starting from the right push the right boulder left into the middle so the middle hits the left boulder and knocks it into the conveyor, when it starts back and just before if hits the middle push the right so it hits the middle at the same time as the left boulder.
If your timing was good they should all be stopped next to each other.
For the top start from the left pushing to the right only this time don't stop walking as you push, keep pushing until all three are stopped like the boulders below.
The rest should be easy.