Although manufactured trusses are more expensive than stick frame roofs when it comes to materials, the labor savings are significant. In addition, if you have a flat ceiling in the home, you can install the ceiling joists and the rafters at the same time, again cutting back on labor. The advantage of stick frame roofs in roof framing shows up when the roof gets more complex. For example, a roof with dormers or a roof with a lot of valleys and hips may be easier to frame as a stick built roof.
In any home, there are a lot of choices and decisions to make when it comes to roof framing. This is just one and something that needs to be decided during the design phase as the details of the framing plan will need to be completed for the plan review. In addition, the engineering of the home will be impacted by the roof design so any changes to the trusses or framing plan need to be run through the building department or other plan review offices.