He calls us to Jehovah...the Jewish God (who is the Creator of the Universe).
The apostles would attend the synagogue on Saturdays and then on Sundays meet for an agape meal and the Eucharist in a home church. You can see this in the book of Acts where they all lived in one community.
So were his 12 apostles, his 72 disciples, and in fact all of the early Church.
As He is the founder of the Church, He can be said to be a "member" of it, in the sense that He is the Head of His Body, the Church. Which was, at the time, the Jewish Christians: as Our Lord told the Samaritan woman at Jacob's Well, "Salvation is from the Jews."
To say "Roman Catholic" is something of an anachronism. The Church was "Catholic," tout court. It was only after the 16th Century that the term "Roman Catholic" gained any currency: there was a party of Anglicans who liked to call themselves "Anglo-Catholics," and they launched the correlative term, "Roman Catholics."--- to pin on the Catholics, who called themselves Catholic.
The Anglicans in England also called the Catholics "The Italian Mission." These terms were meant to be put-downs. That's not necessarily true now, but it was then.
Thank you, by the way, for a good contribution to the discussion.