Roma begins with an indigenous woman named Cleodegaria “Cleo” Gutiérrez working as a live-in maid in an affluent household in the Colonia Roma neighborhood of Mexico City. The family is comprised of the family’s matriarch, Sofía; her husband, Antonio; her mother, Teresa; their four young children, and one other maid, Adela.
When Antonio, who is a doctor, leaves for a conference in Quebec, it’s clear that his marriage to Sofía is on the rocks. As soon as he returns home, he leaves once again for a few weeks.
Meanwhile, Cleo and Adela are together, they speak their native Mixtec. The women’s boyfriends, Fermín and Ramón, typically accompany them to the movies most weeks. However, on this particular day, Cleo and Fermín decide to go for a walk instead.
The two wind up at a hotel where they rent a room, and have sex. Weeks pass, and when they spend another night at the movies, Cleo tells Fermín that she thinks she is pregnant. Startled, Fermín excuses himself to the restroom—never to return. Cleo also confides to Sofía her secret, and Sofía takes her to the hospital to get checked. There, the doctors confirm Cleo’s suspicion.
On New Years, Sofía, Cleo, and her children head to a family friend’s home. Recent tensions over land in the area are the topic of conversation between both the landowners and the workers. Later that night, during the celebrations, a fire ignites in the forest. Everyone must band together to extinguish it before it rages out of control.
Once back in Roma, Cleo takes the children with their grandmother to see the film Marooned. While there, they spot Antonio flee with a young woman in tow. Sofía tries to hide this tidbit from her children. However, her second son is a smart one, and he learns the truth when he eavesdrops on his mother. So, Sofía asks him to not tell his siblings what he’s learned.
Adela’s boyfriend, Ramón, reveals to Cleo that Fermín is at an outdoor martial-arts class. She heads off to confront him. There, Fermín refuses to acknowledge that the baby is his. Instead, he threatens to beat her and her child if she tries to find him again.
With the baby’s due date approaching, Teresa takes Cleo crib shopping, but on the way, they see students gathering for a protest in the streets. These protests quickly these turn deadly when the police start clubbing citizens, and bands of roving youths randomly start shooting at protesters.
After one wounded man runs into the store in an effort to hide from the violence, several youths track him down where they shoot him dead. One of those youths turns his gun on Cleo. She’s horrified to see Fermín is the one pointing it at her. He glares at her before running off. Cleo’s water immediately breaks from the stress of it all.
Teresa has her driver take Cleo to the hospital, but they get stuck in traffic amid all the violence around them. Antonio shows up to give Cleo moral support, but he quickly makes an excuse to not be there, and leaves. The doctors don’t hear any sort of heartbeat in Cleo’s womb so they rush her into surgery. There, they deliver a stillborn girl, and multiple attempts to resuscitate the baby fail.
Back at the homestead, Sofía can’t park their large car in the family’s narrow garage while drunk. So, she buys a narrower one. However, she first plans one last trip in the old one to the beaches at Tuxpan for a family holiday—without Antonio. To help Cleo cope with her loss, she brings her along too. While there, Sofía tells her children that she and their father have separated. Their little holiday away was so he could collect his belongings in peace.
Tragedy nearly strikes at the beach when a strong current nearly sweeps the two middle children away. Even though Cleo doesn’t know how to swim, she wades in to save them. As Sofía and her children affirm their love for Cleo over her selfless act, Cleo breaks down. She says it’s because never wanted her baby to be born.
Once they all return home to Roma, they find Sofía’s home completely reorganized. Cleo is soon back at work, and as she prepares a load of wash, she tells Adela they have much to talk about.