Seems like the ashes storage has been covered well...
About the rocks, unless you are going to use them soon, I wouldn't bother with containers, and I certainly wouldn't spend any money to do so.
Rocks are heavy, and it's easy to fill any plastic container beyond what it is capable of supporting. Half-full in a five gallon pail is about all the handle will tolerate, you can put some more in if you lift by the rim.
Square-ish totes are less strong than round pails, and aren't really up to being lifted with such small, dense stuff in them. Wheeled totes are probably for floors, and aren't any use out in the garden.
All of them are going to fail over time in the sunlight, and you are right back to picking them up again. Without lids, they will collect water and debris, yuk.
Stones are probably the easiest thing to store, since they have so little to go wrong. A pile of rocks will be waiting and ready years from now.
Keeping small stones/gravel "clean" is about all you might want/need to do. Put a tarp under your pile to keep the stones and the soil separate, and cover with another tarp (or the other half of the tarp) to keep leaves and debris out.
Choose a good spot, maybe it's near your next project? otherwise put the rocks somewhere you are certain you won't need to move them unless they are being used!
If you have a
tractor, and want to use
pallets to store stones on for easy moving in the future, use two pallets. One pallet for the rocks, on top of another pallet on the ground. You have just about one year with a single pallet on the ground before it might not be able to be lifted. The double-stack saves the top pallet from sinking into the earth. The bottom pallet doesn't need to be perfect.