Rf value is unique for every solvent system. It can also vary depending upon number of conditions. Its good to purchase standards and try to find out Rf value.    

Dear Patricia,

Carnosic acid and Carnosol are diterpenes and hence they are expected to get elute in non polar mobile phase as you mentioned (hexane :ethyl acetate or pet ether : ethyl acetate). You can get some idea from the literatures but cannot confirm with that. As like the researchers mentioned it can be confirmed only by comparing with the standards. All other modes will remain  rough interpretations.