Always something to avoid
"Rolling" bees is a term that is given to the pinching and subsequent rotating of bees by the action of the beekeeper.
Probably the most common incidence of rolling is when a frame of bees is removed from a box when there isn't enough room to do it. The faces of combs are not flat, so when a comb is taken out of a box the gap gets wider, then narrows, so there isn't enough room for the comb and two lots of bees. If the comb is forced, the bees get pinched and rolled. This can make even the most docile colony become angry.
Very often there is drone comb on the bottom of frames, which is wider than worker, but can't be seen. Forcing a comb when there isn't enough room is likely to kill or damage the queen as well as firing the colony up.
A good handler will make enough room to get the first frame out of a box without rolling bees, but on many occasions I have seen a handler yank a frame out without making room first. This is simply very bad handling that shows little respect for the colony.
I use castellated spacers in my brood boxes and I find it so easy to create enough space. I lift one frame out of the slot, ease it towards me until there is a little resistance, then rest it on the castellation. Do the same with the next frame and I have usually created enough space to remove the next frame. Having lifted it out of the slot, I pull it away from the adjacent frame to avoid rubbing faces and rolling bees.
Although a B.S. National brood box was designed for 11 frames you can just squeeze 12 Hoffman frames in, which many try to do. Because Hoffman frames can't be closed up there is no way of creating space, so bees must be rolled. To avoid this a division board is usually put in the gap between the outside comb and the box. When inspecting a colony this is removed first to create a gap.
Wiping bees off the top bars of frames or the tops of the boxes and putting your hand on the backs of the bees on the face of a comb and moving them sideways also rolls bees.
I have seen handlers, often quite experienced ones too, make enough space to remove a frame, but instead of moving a frame away from the adjacent one, they remove it vertically and rub surfaces, still rolling bees.
Whatever the reason, rolling bees is usually caused by bad handling, but owing to the offending beekeeper often being fully "booted and suited" they don't often realise they are doing it.