Reddened stems on a rose bush indicate a plant infected by rose rosette virus, which will eventually kill it. Remove the plant quickly before it spreads.

The intensely red leaves and shoots that are consistent with rose rosette should not be confused with the normal red growth of some roses that you would see in the spring — but not at this time ...

Symptoms of rose rosette disease include thick, often redder-than-normal stems with many times the normal number of thorns. Stems rapidly elongate and will be more succulent than normal.