Answer: Most hybrid and Knockout roses are grafted onto vigorous root stocks. If the tops of your rose plants died but the roots remained alive, what you are seeing are stems from the rootstock. In the case of the Knockout rose, it's a rambling rootstock. You'll see lots of vigorous green growth but probably no flowers. The rootstock on your other rose could be almost any kind of vigorous rose. It may or may not flower but it won't be anywhere near what you originally planted. I would remove both wildroses and replace them with new plants.
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