I sprayed dead beetle juice on my roses and the beetles stopped coming. I collected the beetles in a glass-wide-mouth-bottle half filled with soapy water. After they died, I put the water in a spray bottle and sprayed the roses. Replenish the water and soap in the glass jar to flip the beetles into it to make some more of the water to spray. I did not use blend the beetles. Let them die from drowning in soapy water. It may help too that no one else in the neighborhood have a lot of roses.
Your roses are beautiful, Buttonwood. Your method is easier. If the beetles come again, I will use your method. Thank you---