Romulan disruptors were a type of hand-held disruptor weapon used by Romulan officers or as mounted weapons utilized on board starships serving the Romulan Empire. They were first seen in the 23rd century when the USS Enterprise entered the Romulan Neutral Zone to steal a cloaking device. (TOS: "The Enterprise Incident")
During the 24th century, the Romulans were using a sleeker designed disruptors that featured various power settings as well as an overload setting. (TNG: "The Next Phase", "Face of the Enemy"; DS9: "The Search, Part I")
The Romulans also had two larger versions referred to as disruptor rifles. These versions were capable of firing a more powerful beam than their smaller counterparts. (TNG: "Unification I", "Unification II"; DS9: "Improbable Cause")
In 2369, Doctor Beverly Crusher was shot from a close distance with a Romulan disruptor but was frozen in time due to several temporal fragments. When the away team, including Captain Picard, Data, Geordi La Forge, and Deanna Troi, was able to return the normal timeline, Troi saved Crusher by pushing her out of the way. The Romulan officer was surprised, but wouldn't shoot at Crusher. He tried to shoot at a female alien who had been posing as a Romulan. (TNG: "Timescape")
In TNG: , Unification II (episode), Spock aims a disruptor rifle at Sela, saying apologetically that he doesn't know much about their settings. According to the novelization of the episode, Sela is prompted to lay down her weapon by the knowledge that Romulan disruptors have no stun setting: high settings will vaporize the target, while lower settings will cause his or her organs to explode.