Same way as usual, except you use concrete or metal for beams, and e.g. http://en.wikipedia.org/wiki/Hollow-core_slab between the beams. For brick, archways e.g. catalan vaults, you can do pretty amazing things with brick archs: http://www.lowtechmagazine.com/2008/11/tiles-vaults.html

> Even if it's a single story, how do you make a roof?

You can do them the same way, though a wood bent to support e.g. a tile roof tends to be more common (having just a wood bent is a far cry from a wood house).