I didn't take a closeup, but I will take more pictures with a different camera tomorrow.
I think I solved the mystery. While walking Winston the pug, I snipped some branches from the wild white roses growing nearby. I think a bird planted one in my rose garden. They have the same form, same blooms, same leaves. I'll have to get some pictures of them tomorrow also. These things can get monstrously big. In winter, it is hard to distinguish them from the blackberries. They have the same sprawling, thorny form, but different colored bard and different thorns.
I am off to search species and alba roses on helpmefind.
