Church fathers

Why does the Book of Concord quote from the church fathers? I have always been told that the church fathers are Roman Catholic.

Many of the church fathers quoted lived at a time before we would recognize a “Roman Catholic Church” (approximately 400 A.D.). Because of that, they would not be Roman Catholic.

Such quotations from church fathers, of course, are not presented as being of equal weight as Scripture. The quotations describe how the early church understood and taught biblical doctrines.