the Son of man is the root of both David and Jesus
Paul, how can Jesus be the root of Jesus as if he descended from Himself....as if Jesus had a beginning. Jesus Himself is the Root and Creator of ALL things. He is the Alpha and the Omega...the beginning and the end. As I already noted above, Jesus is there at the beginning of genealogoies in Luke at the creation of Adam and He is there at the end of genealogies in Luke being born in the flesh through the bloodline of David....the Root and offspring of David.

God bless you

O my Jesus,
forgive us our sins,
save us from the fire of hell,
lead all souls to heaven,
especially those who are in most need of Thy mercy.
~ Fatima Prayer