The bleach solution can be used. However, we typically just wash them off with the hose prior to planting and I have never noticed an issue. You might want to make sure its not Woolly Aphid material, especially if it not common in your area.
Krichberg and I both got some trees from One Green World that had some roots that were rather moldy looking. My two trees both came out of it fine though. I’m not sure how his did. So it may not be to dire, if yours look like ours did last year.