We don't have it for bones, though you can freeze a mesh's rotation and scale.
If your goal is to test out your weights, you can switch to animate mode so your bone manipulations don't wreck your setup pose. You can even adjust weights in animate mode for convenience, even though they really for editing the setup pose. If just doing a quick test, I often just try the bones out in setup mode and then use undo so I don't mess up my setup pose.
Have you seen transform copy? Select some (or all) bones, ctrl+c to copy their pose, then you can later select them again and ctrl+v to restore the pose. You can even select the same number and hierarchy of different bones and ctrl+v. Selecting world or local axes affects what happens when you ctrl+v. For quickly selecting bones over and over again, try selection groups.
Also note that the weights tool remembers its selection. Eg, select the weights tool and a mesh, then select the rotate tool and a bone. When you go back to the weights tool, you'll still have your mesh selection. Likewise, the rotate tool keeps its bone selection. This lets you jump back and forth for editing weights. Remember right click toggles to the last tool you had selected.