I often use tarps and canvas bags, as outlined above. Both can be easier, and less dangerous, than trying to used wheels on a slope.
For lowering heavy loads, there are many belaying/abseiling techniques that work well and are safe if used properly. Do you have any friends into climbing? Also, tree trimmers often use these methods, both for safely climbing and controlled lowering of cut limbs.
Once, we used a heavy,
water filled, lawn roller as a counter weight, attached to a rope and run through a pulley anchored around a stout tree. It was very effective, but it required a lot of diligence, heavy rolling weight is a recipe for injury.
But if you have materials to haul in both directions, a rope and pulley and a couple of tarps could do a lot of the work for you if you can match the weights on the two tarps. As you will have both friction and muscle power to assist, the weights don't have to be exact, just somewhat close.
Or might I suggest my favorite heavy moving technique? Provide some beer for a bunch of thirsty friends....available right after we move those rocks other there.