The Romulans are closely related to Vulcans but are devious and untrustworthy. Both have been around the Star Trek universe since the original series.
Their makeup has changed over the years but less so than the design for Klingons: the most immediately noticeable change (besides the forehead prosthetic) is their wholescale adoption of a particularly unflattering hairstyle.
Michael Westmore was makeup designer and supervisor.
Pel: In Star Trek: Picard Pel (Ayushi Chhabra) is the pregnant daughter-in-law of Raffi Musiker. James MacKinnon was department head makeup & prosthetics; Silvina Knight was assistant makeup department head; Vincent Van Dyke (Vincent Van Dyke FX) was the prosthetics designer; Richard Redlefsen & Alexei Dmitiew were the key prosthetic makeup artists.
Senator Tal’aura: In Star Trek: Nemesis the murderous Senator Tal’aura (Shannon Cochran) was a member of the Romulan Senate who secretly allied herself with Shinzon of Remus. She used a thalaron radiation projector to assassinate the entire Senate thereby setting the movie’s events in motion. Shannon Cochran had played a number of other guest roles in various Star Trek series including the Klingon Lady Sirella. Nemesis also featured Dina Meyer as the Romulan Comander Donatra.
Nevala: In the Star Trek: Voyager episode ‘Message in a Bottle’ Nevala (Valerie Wildman) was second in command of a squad of Romulans who captured the USS Prometheus.
Karina: In the Deep Space Nine episode ‘Visionary’ Karina (Annette Helde) was a diplomat for the Romulan Star Empire who visited Deep Space Nine to be briefed by Starfleet intelligence on the Dominion: she was unimpressed.
‘Romulan’ officer: In the Next Generation episode ‘Timescape’ Picard, Geordi, Troi and Data returned from a Federation conference to find the Enterprise and an attacking Romulan Warbird frozen in time. But things were not quite as they seemed: aliens from a different time-continuum had assumed Romulan bodies, including a female (Patricia Tallman), in order to survive in this continuum. Patricia Tallman was part of the Star Trek core stunt group for some eight years: doubling lead actresses and several guest actresses; playing stunt acting parts as various aliens; and coordinating fight scenes.
Taris: In the Next Generation episode ‘Contagion’ both the Enterprise & the Romulan warbird IRW Haakona, commanded by Subcommander Taris (Carolyn Seymour), traveled to Iconia in the Neutral Zone following the destruction of the USS Yamato. This was the first of several Star Trek roles for Carolyn Seymour, who later played another Romulan, Commander Toreth, in ‘Face of the Enemy’.