It's a little difficult to see the blooms in your photos, but they don't look single to me. They've got more than 5 petals, if I'm not mistaken.
If so, might this be R. rugosa alba plena?
https://www.helpmefind.com/ros...
If I'm wrong, and it really is single, might it be R. rogosa alba?
https://www.helpmefind.com/ros...
