We have a home with a breezeway between the house and garage that is 11 feet wide and 15 feet long with traditional roof trusses that are 24" on center 2x6 constuction. There are roof rafters, again 2x6 that are spaced 16" on center with every third one connected (nailed) to the truss. Question, can we remove the roof rafters to create a vaulted ceiling or are we better off only removing every two out of three and created a coffered ceiling. Wall hieght is 87" with distance from top of wall to peak of roof approximately 24". Obviously we want to open the ceiling so it does not appear to be a long low tunnel.
I think you're mixing up the names of the different parts because to make a vaulted ceiling you would remove joist and not rafters. I don't know the purpose of the rafters/joist that you say are in-between the trusses. It doesn't make any sense. If you have trusses to form the structure then why would anyone install more rafters? I would assume that the rafters were installed for a reason and if you remove that "reason" the structure will collapse.
If you're talking about the horizontal pieces of a truss you cannot remove them or the structure will collapse. They help form the 3rd side of a triangle and without the other side the triangle is all loose and will collapse.