The Collaborative International Dictionary of English v.0.48:

Roof \Roof\, v. t. [imp. & p. p. Roofed; p. pr. & vb. n.
   Roofing.]
   1. To cover with a roof.
      [1913 Webster]

            I have not seen the remains of any Roman buildings
            that have not been roofed with vaults or arches.
                                                  --Addison.
      [1913 Webster]

   2. To inclose in a house; figuratively, to shelter.
      [1913 Webster]

            Here had we now our country's honor roofed. --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Roof \Roof\, n. [OE. rof, AS. hr?f top, roof; akin to D. roef
   cabin, Icel. hr?f a shed under which ships are built or kept;
   cf. OS. hr?st roof, Goth. hr?t. Cf. Roost.]
   1. (Arch.) The cover of any building, including the roofing
      (see Roofing) and all the materials and construction
      necessary to carry and maintain the same upon the walls or
      other uprights. In the case of a building with vaulted
      ceilings protected by an outer roof, some writers call the
      vault the roof, and the outer protection the roof mask. It
      is better, however, to consider the vault as the ceiling
      only, in cases where it has farther covering.
      [1913 Webster]

   2. That which resembles, or corresponds to, the covering or
      the ceiling of a house; as, the roof of a cavern; the roof
      of the mouth.
      [1913 Webster]

            The flowery roof
            Showered roses, which the morn repaired. --Milton.
      [1913 Webster]

   3. (Mining.) The surface or bed of rock immediately overlying
      a bed of coal or a flat vein.
      [1913 Webster]

   Bell roof, French roof, etc. (Arch.) See under Bell,
      French, etc.

   Flat roof. (Arch.)
      (a) A roof actually horizontal and level, as in some
          Oriental buildings.
      (b) A roof nearly horizontal, constructed of such material
          as allows the water to run off freely from a very
          slight inclination.

   Roof plate. (Arch.) See Plate, n., 10.
      [1913 Webster]

WordNet (r) 3.0 (2006):

roof
    n 1: a protective covering that covers or forms the top of a
         building
    2: protective covering on top of a motor vehicle
    3: the inner top surface of a covered area or hollow space; "the
       roof of the cave was very high"; "I could see the roof of the
       bear's mouth"
    4: an upper limit on what is allowed; "he put a ceiling on the
       number of women who worked for him"; "there was a roof on
       salaries"; "they established a cap for prices" [syn:
       ceiling, roof, cap]
    v 1: provide a building with a roof; cover a building with a
         roof

Moby Thesaurus II by Grady Ward, 1.0:

137 Moby Thesaurus words for "roof":
   Dymaxion house, French roof, M roof, White House, abiding place,
   abode, address, adobe house, ancestral halls, apex, barrack roof,
   bonnet, building, bulkhead, cantonment, cap, casa, ceil, ceiling,
   chamber, chimney corner, clerestory, cliff dwelling, coif,
   consulate, cork, country house, country seat, crash pad, crest,
   crib, crown, cupola, dacha, deanery, dome, domicile, domus,
   dwelling, dwelling house, dwelling place, eaves, edifice, embassy,
   erection, fabric, family homestead, farm, farmhouse, fireplace,
   fireside, foyer, gable roof, geodesic dome, habitation, hall, hat,
   haven, hearth, hearth and home, hearthstone, home, home place,
   home roof, home sweet home, homestead, hood, house, houseboat,
   household, housetop, ingle, inglenook, ingleside, lake dwelling,
   lantern, living machine, lodge, lodging, lodging place, lodgment,
   manor house, manse, menage, nest, overhead, pad, parsonage,
   paternal roof, peak, penthouse, place, place to live, plafond,
   prefabricated house, presidential palace, ranch house, rectory,
   residence, ridgepole, roof garden, roof in, roof-deck, roofage,
   roofing, roofpole, rooftop, rooftree, seat, shed roof, shelter,
   shield, shingles, skylight, skyscraper, slate roof, slates,
   sod house, split-level, stopper, structure, summit, surface,
   thatched roof, tiles, tip, toft, top, top floor, top side, topside,
   topsides, town house, upper side, upside, vertex, vicarage