Speaking on the “Director’s Cut” podcast, Alfonso Cuaron finally explained why his longtime friend and DP Emmanuel Lubezski wasn’t the cinematographer for “Roma”:
“Chivo [Lubezski] started prepping [‘Roma’], and I actually planned this film for Chivo. I budgeted this film for Chivo’s thinking. With Chivo, there’s always the same concern and complaint—well, he has many complaints (laughs). The biggest thing since we started making films together when we were teenagers was time. Time to do things. Time to prep the film, time to shoot the film, time to do the Digital Intermediate at the end of the process, he’s always asking for more time,” explained Cuaron.
He continued, “So I designed it for Chivo. The byproduct of that is that we started prepping and I start realizing, ‘No we need more prep time.’ We start looking for locations and I said, ‘We need more shooting time,’ and we kept extending everything until Chivo said, ‘I cannot do this film anymore, I have other commitments’. And that was maybe two and a half weeks before we started shooting.”
No offense to Cuaron, who ended up being his own DP on 'Roma' and shoots the hell out of the picture, but one can only imagine what Lubezski could have done with some of the shots conceived in the film. However, "Roma" is a masterwork and the fact that Cuaron decided to shoot, direct, and photograph the story of his childhood makes it a more personal vision, so there's that.