Reading Romans as about Christians and not about Christians

As I have been going through Romans once again with my Sunday school
class, it has increasingly become evident to me how hard it is – and at
the same time how important it is – to realize that this isn’t a
Christian document.

In saying that, I don’t mean that Paul’s message was not that which
at a later time would be labelled “Christian.” But neither am I simply
pointing out that, when Paul wrote, the label “Christian” had not caught
on yet, and Paul does not use it.

But when we realize that Paul did not have a clear label such as
“Christian” for the movement of which he was a part, it should make us
wonder: Did Paul think of himself as part of a distinct group at all?
Did he simply think of himself as Jewish?