Would permanent and attached seating count in roof calculations?

Based on this reference guide addendum definition, I'd assume that seating can be excluded: "An appurtenance is any built-in, nonstructural portion of a roof system, such as skylights, ventilators, mechanical equipment, partitions, and solar energy panels." It may be helpful to submit a project-specific CIR, as I didn't find any LEED Interpretations addressing this issue.

You're welcome. LEED Interpretation 5676 addresses a similar situation. It states that mechanical equipment covering 30% of the roof can be excluded from the credit calculation, but to reduce heat island effect the project team should consider installing light-colored mechanical equipment. Based on this I'd say you can exclude the roof area covered by the seating in the calculation (and consider using light-colored seating), although if the roof below the seating is SRI compliant it wouldn't matter if you excluded it or not. This LI has not yet been approved or considered for 2009 projects, so the reviewer may consider it appropriate for your project if you were to reference it in your submittal.