You should:
1. Open your project in 8.1 (if it is not too late) and save as PNA; then reference that PNA as the library source. This might cause some problems. Or, open the 8.1 library.pna, and extract the library into folders, and load what you need.
2. replace the missing lib parts with the same or similar ones from the 9 library; as you are mentioneing roof structure elements, you probably used the Roof Acessories API; in this case, the most drastic solution would be to re-create everything.
Djordje
ArchiCAD since 4.55 ... 1995
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