Star Trek: 10 Things You Didn't Know About Romulans
4. Caecilius Est In Horto
If you're now having flashbacks to your school days and the Cambridge Latin Course that (in)famously begins with the phrase of the title (translation: 'Caecilius is in the garden'), then, well, you're welcome! Switch out 'Caecilius' for 'Decius,' and 'in the garden' for 'on the Bird-of-Prey,' and you've got the start of the story of the Romulans on screen. The fact that Romulan society is based on that of ancient Rome is evident, but the links to Latin in the Romulan language are harder to find. Nevertheless, they are still there.
It is Star Trek multi-novelist and co-writer of the episode Where No One Has Gone Before, Diane Duane, who developed the first fully-fledged version of the Romulan language in the 1980s for her (two) books My Enemy, My Ally, and The Romulan Way, which later became part of the 'Rihansu' series. Duane decided that, given the Roman connection, the Romulan language would have a "slightly Latinate" sound, as well as bearing some resemblance to Vulcan.
Duane built a grammar and vocabulary, even designing a computer program capable of generating "several thousand words of Rihansu in a given run" (Rihan is more properly 'the Romulan language' in Romulan). Duane's work has since been picked up and expanded on by fans at the Romulan Language Institute and the Center for Romulan Studies (amongst others).
On screen, the most Romulan we've heard spoken was in Star Trek: Picard's first season. That version of the language was developed by constructed language expert Trent Pehrson. Pehrson did more than translate dialogue, however. He took all the elements of the Romulan language that were considered canon, including elements of Vulcan, and then, as he said on Facebook, "The rest (the majority of the language) I had to construct."
According to Michael Okuda in the Star Trek: Next Generation DVD extra Alien Speak, the Romulan writing system was first devised by a "gentleman named Monte Thrasher" (who also created the Romulan insignia for TNG) as a script that could be composed of symbols made entirely by a "seven-segment digital readout." Okuda and his team added a few extra touches, but that was "basically the thought behind it."