Rose bush leaves can turn yellow when there is an issue with light, water, pests, disease, fertilizer or heat stress, according to Gardening Know How. After yellowing, the bush may lose the leaves entirely.
Lower leaves can yellow when they do not get enough light. There are several pest and disease problems that are characterized by yellow leaves. Leaves can yellow to try to cool the plant from heat stress. Too much fertilizer can "burn" the plant, causing leaf yellowing and drop off. Also, sun rays can bounce off water droplets around the base of the plant, causing yellowing and leaf burn.