I think he's asking if he can tear out sheetrock and insulation have exposed trusses. If this is the case, the answer is yes, but you may end up looking at wires, pipes, and air ducts with roof sheathing for a backdrop. You will also loose your insulation. Exposed ceilings really nee to be designed into the house ahead of time.
Apples or oranges.......... you're not talking about rafters, are you? With trusses, you need the ceiling drywall (or approved material) for fire-code or replace them with cathedral trusses, as said. Page 127+ for rafters, pp.157+ for trusses:
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