Watch: Alfonso Cuaron Discusses the Breakout Stars of 'Roma' (Exclusive)

"Nobody had a screenplay," Alfonso Cuaron says in reference to the stars of his film Roma during an interview in a new featurette about its making. "The actors were learning day by day what we were doing."

He continues, "What I wanted to do was create a moment of truthfulness, a moment that was actually happening. The idea was for the camera to be there to just register those moments."

Cuaron, the Mexican filmmaker who won the best director Oscar for 2013's Gravity, has made a black-and-white, Spanish-language, Netflix-distributed film about his complicated childhood in Mexico City, all without any "household names" appearing on camera — but he says he couldn't be prouder of the work done by Roma's ensemble, which included dozens of Mexican character actors.

Some, like 24-year-old lead actress Yalitza Aparicio, had never previously performed in any forum. Aparicio, a schoolteacher, was chosen over more than 3,000 others who attended open casting calls in her native Mexico, and Cuaron, who previously directed Julianne Moore in Children of Men and Sandra Bullock in Gravity, calls her "the most amazing actress I have ever worked with."

Others, like supporting actress Marina de Tavira, were experienced performers on stage and screen. Cuaron applauds Tavira for being willing to "surrender" to the unusual manner in which he wanted to make this film, "the toughest thing she has ever done."

"The chemistry of all these people together," Cuaron says, made for an unforgettable collaboration, and helped him to tell a story both deeply personal and simultaneously universally applicable. "The film is ultimately about family. It is about women. It is about motherhood."

Roma is one of the Netflix films to receive a theatrical release this awards season, partly to attract elite filmmaker partners and partly to appease awards voters — including members of the SAG Awards nominating committee, who need to turn in their ballots by 5 p.m. on Sunday night — who wish to safeguard the theatrical experience. Roma began rolling out in select U.S. and Mexican theaters on Nov. 21, and the streamer announced Friday that the film will ultimately be released in more than 100 U.S. theaters and 500 more around the world.