The Collaborative International Dictionary of English v.0.48:

Roust \Roust\, n. [Cf. Icel. r["o]st an estuary.]
   A strong tide or current, especially in a narrow channel.
   [Written also rost, and roost.] --Jamieson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roost \Roost\, n.
   Roast. [Obs.] --Chaucer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roost \Roost\, v. t.
   See Roust, v. t.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roost \Roost\, n. [AS. hr[=o]st; akin to OD. roest roost,
   roesten to roost, and probably to E. roof. Cf. Roof.]
   1. The pole or other support on which fowls rest at night; a
      perch.
      [1913 Webster]

            He clapped his wings upon his roost.  --Dryden.
      [1913 Webster]

   2. A collection of fowls roosting together.
      [1913 Webster]

   At roost, on a perch or roost; hence, retired to rest.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roost \Roost\, v. i. [imp. & p. p. Roosted; p. pr. & vb. n.
   Roosting.]
   1. To sit, rest, or sleep, as fowls on a pole, limb of a
      tree, etc.; to perch. --Wordsworth.
      [1913 Webster]

   2. Fig.; To lodge; to rest; to sleep.
      [1913 Webster]

            O, let me where thy roof my soul hath hid,
            O, let me roost and nestle there.     --Herbert.
      [1913 Webster]

WordNet (r) 3.0 (2006):

roost
    n 1: a shelter with perches for fowl or other birds
    2: a perch on which domestic fowl rest or sleep
    v 1: sit, as on a branch; "The birds perched high in the tree"
         [syn: perch, roost, rest]
    2: settle down or stay, as if on a roost