Question
I planted knock out roses last year.  The suffered a little freeze damage, but overall they have made a come back.  However,
we have had a drought, then a lot of rain....now I am noticing yellow leaves on the bush.  Is it too little/too much water?

Answer
Your description of your weather is ideal conditions to put roses under stress. That is what has happened and so made their leaves go yellow. They got too much water and then they were not able to adjust to the heat. The roses don't have any disease and will come back to normal when things even out. Just give them time and they will produce normal green leaves.