Most orchids don't make new roots on old pseudobulbs. Those pseudobulbs provide the reserves of water and nutrients for the new growth, which will include new roots. If the old ones have a few roots, so much the better. So it is very important to get the plant into good media before the new growth, so that the new roots won't get disturbed once they start growing.
I don’t know if it did any good, but I did a heavy misting of the root zone of my rootless wonders (the plants were outside with great air circulation so water persisting in the crown wasn’t an issue) until they recovered. They didn’t have any roots in the media and the top where the root stubs were dried out fast so this was my solution to keeping some moisture available by the root stubs.
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