To elaborate a bit, space frames are usually two way trusses as you suggested in your first post. The top and bottom chords are offset, so the whole roof is formed by a maze of triangles. There are a number of proprietary space frame manufacturers. Most use circular hollow sections for all members. The joint design is the tricky part, and again, there are quite a few proprietary solutions, the most elegant of which are also the most costly.
What do you or your architect intend as the roofing material? The selection of a structural system would depend to a degree on how the roof slopes, the amount of secondary members required, etc.