Mad bees

The roses (Rosa rugosa) in our hedge have lots of flowers on them now. Today, I could hear bees in several flowers, sounding as if they were trapped as they were buzzing madly. On closer examination, each bee was whizzing round the circular inside of the flower, sometimes rolling over and over (head-over-heels fashion) presumably to cover themselves in pollen from the stamens. I have never noticed this behaviour before - they appeared to be quite frantic. I could only get clear photos of them when they paused for a moment.