Question
This time last year we had a problem with fine hair-like roots just under the surface around the rose bushes.  We have dug out the roses, replaced the soil with new garden soil and planted some of the old bushes and new ones as well.  Imagine our disappointment today when fertilising around the bushes, to find the same problem starting again.  The garden is well mulched with sugar cane mulch and notice that the small hair roots are sapping all of the moisture from the soil.  We have another larger garden only about 15 yards away that does not have this problem at all.  The problem garden has nine roses and are spaced approx 1 mtr apart (similar to the larger garden.)

Answer
Two things could be going on here. The first one is that when you fertilize a rose too much and also don't water too deeply, then the fine feeder roots come to the surface and can spread all around the base of the rose bush. They will also deplete the moisture in  the mulch. The other is an infection called Honey Fungus. This is quite common in the rose garden and is caused by very small toadstools. However the toadstools don't always appear and all that you see are the fine, white hairlike threads around the base of the rose. Mulches encourage this disease because they keep the ground moist and cool. The honey fungus spreads all over the roots but because it is a dark brown tends to look the same as  the smaller roots. If the area around the rose smells like mushrooms then that could be the problem.  To keep honey fungus under control you have to burn any plants growing in it and also dig out the soil to the depth of the plants roots an get rid of it. However Honey Fungus will kill a rose and if your roses are doing well then hopefully the white roots are only the feeder roots.