Mine did the opposite of rotting. They dried up and died for lack of moisture, even though other roses in the same beds responded well to watering. When I dug up the gopher cages to dispose of the dead roses, I emptied the "soil" from the cages onto a pile of weeds I didn't have time to pick up before the latest series of rainstorms began. It resembles dry sawdust. After days of storms producing inches and inches of rain, the weeds in the pile are a gloppy mess, but the "soil" from the rose cages is still dry!
As I said before, I think it depends on the type of bark that's used in the mixture. The dead and dying roses were in three deliveries from Roses Unlimited, but other roses from RU, purchased at different times, are doing fine. I have to conclude that some bark-based media are harmful to planted roses and some are not, but I'll be removing all bark in the future just in case it came from a bad batch.
