There are a lot of right ways to grow roses and few absolute rules, because the roses always seem to be able to break the rules. One of the absolute rules is that roses don't like wet feet, so all of the comments above about the very real possibility that you are drowning your rose are spot on.
Fresno has a hot dry climate in the summer. Overhead watering after the temps have reached 85 degrees is actually very beneficial for your rose in that it helps the plant combat the high transpiration rate ... the loss of moisture in the top growth during the hot days of summer. After temps have reached 85 degrees black spot spores are inactive so you don't need to worry about that fungal disease which is the "why" of the recommendation not to overhead water roses. The key point here is "dry" climate. In climates that have high temps in a moist climate can have the same high temps, but they have higher disease pressure because fungus diseases love the moist climates.
A plant can only bring up so much water from the root zone and you will see the top growth wilting even with a well watered rose if the plant's top growth is losing more moisture than it can bring up to the top growth from the roots. Usually, that wilting will disappear overnight as the temps drop and the plant catches up. Overhead watering allows the rose to absorb moisture through the leaves. Also, by "washing" the rose, you are helping to avoid a spider mite infestation because they breed like fire in hot and dry conditions. Washing your rose regularly breaks the breeding cycle of this pest.
There is no need to amend your soil unless it is hard clay where the roots cannot expand outside of the rose hole or very sandy and will not hold moisture. If you put compost in your planting hole when you plant the rose, it will decompose and the rose will sink. If you follow nature's lead and put the compost on top of the soil, as it breaks down, it will feed the soil around the rose. Of course, mulching is part of maintaining a healthy rose in your climate and as the mulch breaks down, it, too, will feed the soil.
I garden in the same hot and dry conditions you have in your climate. If I am dealing with a stressed rose ... and a rose that has been drowning can be considered a stressed rose ... I would dig it up and plant it in a large container with well draining potting soil with no fertilizer amendments and just water it until I see new top growth. This gives the plant the chance to grow a new root mass. The first roots to rot are the feeder roots which pull moisture and nutrients up to the top growth and the food created by photosynthesis back to the root zone. My preference ... and we all learn what works in our climates and develop preferences ... is not to plant a rose into the ground until it has a solid root mass.
Do not fertilize until you see new top growth. That tells you the rose has grown new feeder roots and the root system is operating correctly. Then lightly feed it with a soluble liquid fertilizer weekly because the new roots can be easily burned by normal strength fertilizers. Make certain that your container drains well and lift it off of any hardscape or surface to insure that the container does not hold excess water. Keep the plant moist ... not wet and don't allow it to dry out between waterings.
In your climate, you can plant the rose in the fall when the temperatures are lower and there is less stress on the newly transplanted rose and your rose should have developed a healthier root mass while it was growing in the container.
When you prepare your new hole, do what is called a perk test. Fill the hole with water and ideally it should drain within two hours. If it drains faster, that tells you that you may want to amend your planting soil to slow down the drainage. Plain ol' cat litter will do the job. Again, test for drainage. If it doesn't drain within two hours, as long as it drains overnight, your rose will be fine. If it doesn't drain overnight, you need to make a bigger hole and deeper hole. You may have a layer of hardpan under the place where you are siting the rose and that needs to be broken up to get the desired drainage.
Iceberg is a tough rose. It's a rose that LIKES to grow, so there is a very, very good chance that you can bring your rose back to health and have a glorious plant for your garden.
Here's a link to an Ezine article on HelpMeFind written by Kim Rupert who also grows roses in a hot and dry climate. You can pick up some tips on how to prune the rose to avoid disease.
http://www.helpmefind.com/gard...
I have made plenty of mistakes in learning how to grow roses well, especially once I moved to a new climate. One of the greatest things to know about roses is that when they are happy, they grow like weeds.
Smiles,
Lyn
