This is the work of a creature known to me as a cutter bee. I have never seen one. Apparently, they are very small. I have no idea what purpose they serve in the garden other than destruction.
This rose is the magnificent Dark Lady by David Austin. By the time this bee is done she will have lost over 75% of her leaf surface by my reckoning. Exactly how an herbaceous plant that feeds in part through it leaf is not harmed by losing leaf tissue is beyond me, but there are people who will swear that this bee does not harm the rose. But hey, I am not an entomologist, a botanist or a biologist. I am just a rose gardener who has spent the better part of 50 years growing and caring for roses. I can honestly say that I have finally met a challenge that makes me wish I had never planted a rose on the High Plains of Colorado.
As near as I can tell this “bee” is active from mid-June to mid-August by which time it has completed its nest and becomes dormant. It appears to engage in leaf cutting – the perfect semi circles you see – throughout most of the day. It seems to attack two or three roses in a garden most viciously. I have not been able to discern which roses are immune save miniatures. Perhaps it is the proximity to the ground that discourages the creature from praying on the smaller roses.
If you are planning a rose garden, check with your gardening experts to see if this pest is indigenous in your area. They may have more information about which rose to select to discourage the cutter bee. Once they start there is no getting rid of them, and for my part I find this heartbreaking. While the bloom is intact, the beautiful foliage is disfigured, and the rose appears to my non-expert eye to be weakened in subtle ways from season to season.