Principally you need a wide angle lens, this means you can get a lot of roof in, even if you're very close!

Wideness is determined by the focal length of a lens (which is to do with the optics and not necessarily the physical length of the lens). If you want numbers I'd say 28mm equivalent is a minimum (you'll be unlikely to find anything much wider than that in a compact). The word equivalent is important here, since the relationship between focal length and wideness depends on how big the camera sensor or film is. Equivalent focal length means the number is adjusted to match 35mm film/sensor.

If you get a DSLR (of which the entry level models such as the Canon 1000D or Nikon D3000 will do the job well enough for you) then you can go wider. There are other options I'm sure owners of other brands will chime in and offer you their opinions.

To get the equivalent focal length with these cameras you have to multiply by 1.5 (Nikon) or 1.6 (Canon) so to get the 28mm equivalent focal length figure you need around a 17mm. The lens that comes bundled with these cameras should be about that length.

As I stated getting a DSLR lets you go wider, Canon offer a very good 10-22mm zoom lens (16-35 equivalent) and Nikon offer a 10-24 which is a similar range.