Probably now now while they are busy flowering - having said that, I have moved things when you shouldn't and got away with it. If it must be done now, prepare the new place for them first, dig them up with as much soil and root as possible, and drop them straight in the new place. Give them a good watering, and - and this sounds dreadful but is needful - remove as many flowers as possible. You canot ask the plant to make new roots, move to a new position and support flowers as well, too much to do. If yu can wait a while, then when the flowering has ceased, cut the rock roses back and move as before. Better yet, do them in spring, but I suspect that will be too far away for your needs. You can grow herbs in pots while you wait, in fact many of them do as well, if not better, in pots than in the ground. Which herbs do you hope to grow? Some need moist conditions and others anything but - and it may be better to do those in the autumn too - but I know how it is when the mood strikes.