June
What was the condition of the soil? Were the roses roots sitting in damp
soil?
If we have an open hole - not planted yet - it will hold water for
several weeks or more. If the hole is filled, not as much water
gets in - but the soil is damp.
Our roses like it just fine.
I think you might have had something eat the roots or a fungus rot them.
Remember don't use old rose soil for a new rose. Something goes on.
Martin