Question
We live in Tampa, FL.
We have 15 knockout rose plants, 10 on one side of yard 5 on the other, about 20 feet apart, roughly same amount of sun/shade and watering.
The grouping of 5 rose plants is doing well, the group of 10, within 3 days, have 90% of leave turn brown/gold.
HELP...
Thanks,
Ernie

Answer
One of the reasons roses turn brown and their leaves go yellow is because the roots are complaining about their soil conditions. The other main reason is that some sort of chemical ( including fertilizers) has burnt them. If the roses were all purchased from the same location then it is definitely something to do with their growing conditions. A few days of hotter weather will also cause what you describe in some roses. I know the hype on Knock Out roses suggests that they are iron clad bullet proof but that is really just advertising hype. They are roses and they will re-act to unfavourable situations just as quick as any other roses. As an example. If you put in the soil, or even on top, some fertilizer, they may have re-acted to that. Newly planted roses don't need anything until after they have bloomed the first time and then they need nutrients. From my many questions about Knock Outs, they seem to dislike insecticide or even fungicide sprays, especially the three in one types. Because I am unable to see the roses, I am just throwing out ideas for you that may have irritated your roses. I am assuming that the growing  conditions are really not the same on the other area where the Knock Outs are slowly dying back. Again, if they are newly planted you must water daily because in transplanting even from a pot you put a rose under stress. I know you said you watered them but sometimes the water doesn't seem to penetrate the potted type soil as many growers use perilite which can dry out rose roots very quickly when planted in the garden soil. I would dig down and see just how wet the soil is. Again I am guessing that they are newly planted, but roses when planted even if they are in pots, at this time of year, usually don't do nearly as well as when planted in the fall or spring. If when you scratch the canes and the bark is green then they are not dying just complaining. Keep watering well and they will come back once they settle into their new environment.