Roman is a calculating, cunning person, who is deceiving his friend and has a distinct agenda for his future when he is introduced on the show. While he is first portrayed as at least somewhat affectionate with Petra, albeit a Sin Rostro contact, he is later seen to be violent in nature even towards her and tells Petra much later in Season 1, how he murdered his twin brother in cold blood.
Roman is first seen when he introduces himself to the wait staff. He was also having an affair with Petra, a fact that was uncovered by the police when they put eyes on him after he was named by Cortez to be Sin Rostro's contact. After Michael Cordero realized who Petra was, he told her to end the affair. She tried to, but Roman grabbed her by the neck so she lied that she was testing him to see if he'd fight for her. She left his room, but the man she thought was Roman was killed before she ever saw him again.
Following Roman's death, Rafael gets in contact with who he believes is Aaron Zazo, his identical twin brother. He is introduced as a a Jain (a follower of Jainism, an Indian religion that didn't want to do violence), relaxed, friendly and extremely respectful to everyone he comes into contact with – including all living beings such as spiders. He grows closer to Petra but she eventually realizes he's not who he's claiming to be. Rafael doesn't believe her suspicions so she contacts Michael who sets up cops at The Marbella to survey their dinner, as well as test his finger prints. Although just as the results come in and Michael realizes Aaron is really Roman, he takes Petra away in his car and reveals he knows she has figured out who he is. He brings her to a secluded cottage and reveals he killed his brother, the real Aaron, in order to fake his own death. Petra sleeps with him in order to get to his phone and calls the police. Before they show up, she is confronted by Roman who starts chasing her. He is accidentally impaled when he runs towards Petra who's holding, mirroring his brother's death. 
Roman went to college with Rafael and they roomed together. In some ways, Roman encapsulates what used to be Rafael's behavior, the difference being that Rafael was running away from a painful childhood and Roman actually becomes a criminal working for a drug lord. The two seem close, as Rafael confides his feelings about wanting to divorce Petra to Roman, showing that Rafael considers Roman a friend, before finding out about he is sleeping with Petra and being a murderous, raving lunatic.
Rafael helps who he believes to be Aaron Zazo escape from alleged captivity by paying a ransom (whether that money went to Zazo's plans to snatch Sin Rostro's regime out from under her is never stated, yet very probable).
Roman and Petra were having an affair while she was married to Rafael. Petra later tried to end it but after she turned violent and grabbed her by the neck, she pretended that she was just testing him to see if he'd fight for her. Shortly after, Roman was thought but when Roman returned as Aaron he got close to Petra, claiming he wanted to know more about his deceased brother. She admitted to him that she had genuinely fallen for Roman but loved Rafael more. They get closer and share a kiss but Petra realizes he's actually Roman. He kidnaps her and confesses all to her. She pretends to want in on his plan and sleeps with him to get to his phone and escapes but he comes after her. In the end, she accidentally kills him when he runs towards her, impaling him with a fishing rod.
- Rafael and Roman were college roommates
- Roman's nickname is Zaz.
- Aaron and Roman were estranged.
- Rafael didn't know the name of Roman's brother.
SEASON 1 (9/22)
- Pilot • Chapter Two • Chapter Thirteen • Chapter Fourteen • Chapter Fifteen • Chapter Sixteen • Chapter Seventeen • Chapter Eighteen • Chapter Nineteen
Notes and references