If it is truley crown rot then the crown would need to be soaked, not just the roots. What are planning to soak them in?
What I do is either dig up and soak in a banrot/subdue maxx mixture; I cover the whole thing with it. Or if I leave it in the ground I soak everthing that is exposed and just keep pouring/spraying the ground till it's saturated. If you are using a bleach solution it's the same way.
If there is any mushy stuff on the crown you need to remove as much as you can then soak. And yes, plant back in the ground with the crown exposed and DO NOT plant back in the same place. Either treat that area and wait awhile to replant there or wait until next year to replant. The fungus/bacteria (depending on which rot it is) is naurally occuring in the soil so replanting there can just re-introduce the problem.
Sometimes it won't help no matter what you do even if there are good roots there. If the crown is too far gone the roots won't be to far behind. I have had some that you would think is dead and gone and then a few months later tiny fans start emerging from the tiniest piece of crown left unaffected so you just never kn ow.
