The white flower looks to be Phlox Paniculata David rather than white roses.

There is white phlox elsewhere in the garden, however in this particular area it is the single white roses that are flowering, the photo is taken in early June several weeks before the phlox would have begun to bloom.

This is absolutely lovely! So nicely done. What I love about it is the juxtaposition of the Hydrangeas (is that Endless Summer?) with the more meadow-y flowers. The white (H arborescens?) in the background shows up the blues nicely, which otherwise might recede too much. Inspiring -- thanks for sharing with us all.