The Collaborative International Dictionary of English v.0.48:

Roughleg \Rough"leg`\, n. (Zool.)
   Any one of several species of large hawks of the genus
   Archibuteo, having the legs feathered to the toes. Called
   also rough-legged hawk, and rough-legged buzzard.
   [1913 Webster]

   Note: The best known species is Archibuteo lagopus of
         Northern Europe, with its darker American variety
         (Sancti-johannis). The latter is often nearly or
         quite black. The ferruginous roughleg (Archibuteo
         ferrugineus) inhabits Western North America.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rough-legged \Rough"-legged`\, a. (Zool.)
   Having the legs covered with feathers; -- said of a bird.
   [1913 Webster]

   rough-legged hawk. (Zool.) See Roughleg.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rough-legged hawk
    n 1: large hawk of the northern hemisphere that feeds chiefly on
         small rodents and is beneficial to farmers [syn: rough-
         legged hawk, roughleg, Buteo lagopus]