The Collaborative International Dictionary of English v.0.48:

Rockrose \Rock"rose`\, n. (Bot.)
   A name given to any species of the genus Helianthemum, low
   shrubs or herbs with yellow flowers, especially the European
   Helianthemum vulgare and the American frostweed,
   Helianthemum Canadense.
   [1913 Webster]

   Cretan rockrose, a related shrub (Cistus Creticus), one
      of the plants yielding the fragrant gum called ladanum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rockrose
    n 1: any of numerous varieties of helianthemums having small
         rose-like yellow or white or reddish flowers [syn:
         rockrose, rock rose]
    2: small shrubs of scrub and dry woodland regions of southern
       Europe and North Africa; grown for their showy flowers and
       soft often downy and aromatic evergreen foliage [syn:
       rockrose, rock rose]