Here is what my gardening book says to do, hope it helps.

Propagating Helianthemum or Rock Rose should be done every 4-5 years because the plant becomes woody so in the spring dig up the plant and divide the root crown and discard the woody part and transplant the siblings.

Thanks, so we cannot make from cuttings??

You should be able to take softwood cuttings now, from late spring to early summer, Derek.

This is where using a common name is a problem do you mean Helianthemum or Cistus? Both of them have the common name of rock rose... If you do mean Cistus then you can propagate from semi ripe cuttings in July or early August.

Select non-flowering side shoots and tug them from the main stem, pare back the heel of the bark to about one/eighth of an inch and dip the cuttings in hormone-rooting powder. Shorten them to 7 - 8cm in length removing lower leaves and unripe stem tip.

Plant the cuttings to half their depth, approx 5cm apart, round the edge of a 10-12cm pot, we put potting compost in the bottom quarter of the pot and then fill up with sand (others will use different growing mediums);
water in and place in an unheated propagator.

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If you have Helianthemum, then what I said above is correct, Derek.

If you do not mind getting a variety of colours then seed of Helianthemums is dead easy. Too easy, ours self seed around if we do not cut them back after flowering.

thank you.