Roses, like every other living organism on this earth, must have water to stay alive. Roses are very fond of water and require one to two inches of it every week. In periods of hot, dry temperatures, even more may be needed depending on the size of the bushes as well as whether or not they are mulched. In spite of their need for an abundance of water, roses hate standing in water so it is important that the gardener provide adequate drainage for the rose bed.
There are many myths about the relationship of roses and water. Here are a few of the myths followed by a rebuttal:
Check the depth of your watering to make sure that the moisture is reaching the root system which, for established roses, is quite large. For large roses, if water penetration of the soil is no more than 8 inches, longer watering sessions are needed. Remember that the original planting hole located the roots at 15 to 18 inches below ground level so water which does not reach that level will only encourage the growth of roots so close to the surface that they will be at risk from the weather or excessively vigorous cultivation. Miniature roses have shallow roots so watering to a depth of 8 inches will be adequate for them.
There are many ways to provide water for the roses from hand watering (a water wand is good because it gently deposits a large amount of water in a limited space for easy access to the roots) to various drip systems or even individual bubblers for each plant. The so-called soaker hoses can do a good job inexpensively but only if allowed to run long enough to reach the root zone. Let the rose approve the amount of water it receives; too little will cause the leaves to be limp and sagging; too much will starve the rose of oxygen and its leaves will turn yellow and drop off.