Important topic. Here are my two cents, based on my observations and studies. Let me first propose a different analogy: not a ball rolling downhill, but a drop of water in a sea whose tides are everchanging. The drop can't control the sea, and resisting the ebb and flow of the waters is not only futile but painful.
Another analogy is the cog in a machine, or the cell in a body. Can the cog control the operation of the whole machine, or the cell control the body? No. They fulfill a purpose in a larger structure and they're compelled to behave in very specific ways, they can resist this no better than the drop can resist the sea.
So where's Free Will in all this? In gaining awareness and thus responsibility of our own role in the story. The drop, the cog and the cell all have a choice: they can view this larger structure in which they're immersed as a prison, or they can see it as a home. They can either accept their function and flow naturally through the happenings around them, or they can resist it and suffer inexorably.
In other words, Free Will isn't about controlling the path, but about electing how to approach that path. Eventually, with sufficient exploration, we learn that there was never any difference between the drop and the sea, the cog and the machine, the cell and the body. They're not separate entities. Then Free Will, as a concept, ceases to be relevant.