The Collaborative International Dictionary of English v.0.48:

Roguish \Rogu"ish\, a.
   1. Vagrant. [Obs.] --Spenser.
      [1913 Webster]

            His roguish madness
            Allows itself to anything.            --Shak.
      [1913 Webster]

   2. Resembling, or characteristic of, a rogue; knavish.
      [1913 Webster]

   3. Pleasantly mischievous; waggish; arch.
      [1913 Webster]

            The most bewitching leer with her eyes, the most
            roguish cast.                         --Dryden.
      [1913 Webster] -- Rogu"ish*ly, adv. -- Rogu"ish*ness,
      n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

roguish
    adj 1: playful in an appealingly bold way; "a roguish grin"
           [syn: devilish, rascally, roguish]
    2: lacking principles or scruples; "the rascally rabble"; "the
       tyranny of a scoundrelly aristocracy" - W.M. Thackaray; "the
       captain was set adrift by his roguish crew" [syn: rascally,
       roguish, scoundrelly, blackguardly]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "roguish":
   arch, base, blackguardly, degraded, devilish, elfish, elvish,
   foolish, full of mischief, high-spirited, impish, infamous,
   knavish, mischief-loving, mischievous, notorious, playful,
   prankish, pranksome, pranky, puckish, rascally, recreant,
   reprobate, scampish, scapegrace, scoundrelly, sportive, trickish,
   tricksy, tricky, vile, villainous, waggish