Can you post a pic? That might help. Knockout roses can put out new growth that mimics RRD. I would be cautious before I decided that was really the problem. I have seen suggestions from knowledgeable sources that say you can cut back the branch and see if it the damage shows up again.

I lost about 30 roses to RRD here in Blanchard. A friend in Edmond lost upward of 100 plants. I agree that you should watch and wait. If you see the classic "witches broom" growth you'll know for sure. Here's a link to a good photo. Because I had so many affected I was brutal in my killing, as was my Edmond friend. We both had all varieties of roses affected. We had huge collections from Heirloom Roses in Oregon, but the virus came from a few plants bought in Edmond and spread by the mites.http://nicolewarduk.blogspot.com/2012/04/disease-resistant-knockout-rose.html