Hello,

It seems less like a coincidence than it does a problem with this specific area of your property. Based on the information provided I can only suggest some investigation into the area the hydrangea and rose were planted so that the reason for the plants dying can be identified. 

What is the drainage like in the area where the shrubs were planted? Does water stand in this spot after a heavy rain, and it the answer is yes, how long does the water sit? Root rot can kill a plant after repeated soakings.

Have you had your soil tested at any time in the last 6 years? Deficiencies of nutrients, or herbicide run off could kill plants over time. The Logan County Soil and Water Conservation District offers testing services: https://www.co.logan.oh.us/788/SoilWater-and-other-Ag-Lab-Analysis

You did not mention any disfigurement of leaves, or defoliation of the plants. If you see damage on any living plants that is similar to what you might have seen on the dead rose you could send samples for diagnosis to the C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic, email questions to <personal data hidden>, and read more about the submission process at:    https://ppdc.osu.edu/submit-sample

I hope that you can use this information to begin to work out what is killing the shrubs planted in this area.

Kind Regards,