Be patient. Over the years I have seen people thy lots of things that really don't influence the process at all. Since it is an auto-immune process that will burn itself out over a 4-8 wk period in most cases i now encourage patients to ignore it. The treatment should never be more trouble than the disease.
Sunlight, icepacks. Pityriasis rosea is frustrating because we don't have any great treatments to knock out the rash right away. Usually treatment consists of calamine lotions, topical steroids, benadryl, (diphenhydramine) sometimes Erythromycin is tried. If you want all natural - some exposure to uv light could help just a little, and ice/cool packs for the really itchy areas. Good luck!