Question
I bought my home 6 years ago, and 10 rose bushes came with it. The neighbors at the time told me that the plants were about 50 years old. I have done basic care for them and they seem quite healthy. Is there anything special that one needs to do for older plants? The root system appears extensive obviously. How does surface applications offertilizer ger all the way down to these old roots?

Answer
Roses have two types of roots. Try and imagine a ballerina. From the waist up is the top of the rose plant, the legs are the anchor roots and the  ballerina's skirt are the feeder roots. When you fertilize a rose it is the feeder roots that do all the work and they are usually quite near the surface. The very deep roots are anchors and although  they two may have a few feeder roots on them, basically the ones near the top are the ones that do all the work in feeding the rose and taking up the water. If your roses are looking healthy then don't change anything as you are doing what is right for the roses.