Source : Webster's Revised Unabridged Dictionary (1913)

Roughen \Rough"en\, v. t. [imp. & p. p. {Roughened}; p. pr. &
   vb. n. {Roughening}.] [From {Rough}.]
   To make rough.

Roughen \Rough"en\, v. i.
   To grow or become rough.

Source : WordNet®

roughen
     v : make rough or rougher; "rough the surfaces so they will
         stick to each other" [ant: {smooth}]