I agree with your assessment . . . did notice Roma interjected herself quite a few times in the movie. A narrator filling in the gaps would be helpful to a non-believer who has not read the Bible. I have not seen The Bible series so is Son of God a splice job of it?
The reviewer suggests there is such a narrator, at least at the start. And yes, Son of God is EXACTLY that -- the footage was filmed at the same time as The Bible miniseries. They knew they would be following up with this.