Roof framing has undergone a quiet revolution over the past half century. Trusses are gradually replacing the conventional rafters, to the point that nowadays more than 80 percent of new residential construction uses trusses to support the roof.
 

Why has this change occurred and what are the advantages and disadvantages of rafters vs trusses? Because they're pre-made to your building specs offsite, often via automation like computer-driven saws, they are much faster and cheaper to install than rafters.