Toss any collapsed, mushy or mostly devoured rhizomes into the garbage can. Make a pile of those you're going to save. Grab one and cut the fan to 4", flip it around in your hand, grab all the roots like a barber grabs a hank of hair and in one cut trim a third off the roots. Do this over a bucket so you can collect all the fan and root snips and remove them from your property. Next scrub each plant with undiluted bleach, immediately splashing each in a bucket of clean water. Spread them on the lawn and rinse them all again thoroughly with a hose. This takes care of any disease organisms that might attack weakened rhizomes. An alternative to individual scrubbing is to soak rhizomes in a solution of one part bleach to nine parts water for an hour. Remove and rinse thoroughly.
I personally think bleach is a bit tooooo severe for any plant tubers or roots but then again I have never used this and remember there are all different strengths of bleach on the market, but also, after you do any treatment to a plant, you need to make sure the soil is bug free or fungal free from whatever has been growing in that same spot. You should never replant Roses in the smae spot as you grew them before as you would end up spreading any disease that had harmed the Roses before and I go along with that for most plants that will be growing in the same spot for years, it's called garden hygene and a lot of people forget about soil cleaning.