Warped rosewood back blank
 

I have a rosewood back & sides which I pulled out today and found that the back halves have gotten quite cupped. Not sure if this means the wood is unusable or if there is some way to remove the warp? Does this mean the wood has been improperly dried and is not going to be stable? Thank you

We'd need photos to provide any meaningful input.

Could be the grain, could be slab cut, could have been improperly stickered...

The problem with the distortion is usually the difficulty getting it uniformly thicknessed. Once it is, it can be braced and is a non-issue. if it is mild, spritzing the cupped side and letting it heat/dry in the sun can be enough.

They may have been cut at a different humidity level than you have now. I have straightened wood out as Bruce said, by adding moisture to one side and then thicknessing and joining once they were flat enough.

This could be the result of storing the wood flat, with only the upper side exposed to the air. Warping of thin wood can occur if the moisture content is different on the two sides. In that case, the side that is drier will tend towards being concave. The fix may be as simple as flipping the wood over. If it warps in the other direction, you know that the moisture level in the wood was not in equilibrium with the relative humidity of the air.

I agree with John Arnold. Have you been storing it elevated on sticker blocks/bars in such a way that air is able to pass completely around the wood and it can “breathe” on all faces? Are you also monitoring RH and temperature of the space you are storing it in? IME it should be no higher than 35% RH and no hotter than 80•F.

As noted above, most likely. Let it breathe.