Complex sentence: Patchett did not know much about opera prior to writing the book, although she has stated that the character Roxane was modeled on Karol Bennett, an acquaintance of hers who was an opera singer.
Split into simpler sentences: Patchett did not know anything about opera prior to writing the book. Patchett has stated that the character Roxane was modeled on Karol Bennett, an acquaintance of hers who was an opera singer.