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Glue for what? To attach the plywood to the 2x4s, or to attach the roll roofing to the roof? Is this a cold smoke or do you intend to get the temps higher in the smoker?
Like Al said "what for" if you want to connect the plywood to the wooden studs use screws or nails. Now you could throw s tin on the top for he rain but other then that I wouldn't use glue.