Hardcore fans know what to look for when they settle into theater seats for a Gilbert and Sullivan operetta. There is almost always a case of mistaken identity, the arrival of the Union Jack, syllabically outrageous lyrics, the patter song (and its encores). If the company is the Gilbert & Sullivan Society of Hancock County, theatergoers also might find themselves looking for Roland Dube, who has been a member of the company for 19 years.

In the current production of “Ruddigore,” on through Sunday at The Grand Auditorium in Ellsworth, Dube plays Sir Despard Murgatroyd, a character part that transforms from a moustache-twirling villain to a good-deed doer in the course of the show.

It would take a foot-long scroll to list all Dube’s G&S roles. Last year, he was the Pirate King in “The Pirates of Penzance” and rode a boatswain’s chair elevated to the back of the theater’s third-floor loft and lowered to the stage in the front of the theater.

In reviews, Dube has been called “a G&S machine,” “the popular favorite,” “lively, limber, flamboyant” “one of the dependable treasures of this troupe” and “a star that never outshines his welcome,” and “a bright spot in an already shining cast.”

Outside the G&S oeuvre, Dube has played Benjamin Franklin in a community production of “1776” and Ali Hakim in “Oklahoma!”

“Roland is very easy to work with,” said Dede Johnson, artistic director for the G&S Society. “He’s a good sport and is game to do just about anything I throw at him. He is also a marvelous actor.”

Johnson remembers Dube’s remarkable personal shift, the one in which a shy math teacher became one of the most audacious performers in a quirky theatrical group.

“Oh God, he was so shy and quiet,” recalled Johnson. “He’s not anymore. He just wasn’t terribly comfortable or remarkable. And every year he got better and better and better. He moved from secondary lead to primary lead to playing the real character parts.”

Johnson is not the only one who has noticed Dube’s growth through the years.

“Roland’s a perfectionist,” said his longtime friend and 18-year G&S compatriot Dotti Schaller. “He was never sure of himself and he’s still a wreck backstage, but he’s totally composed onstage. As soon as there’s an audience, he’s a different person. He comes alive.”

Witnessing Dube’s witty and whirling stage performances, testaments to his shyness seem far-fetched. But spending time with him in other settings, for instance in Room 202 of the William S. Cohen School in Bangor where he teaches middle-school math, the bashfulness surfaces. He is modest and only quietly fussy about any discussion of remarkable talent. To him, the life story is simply that he was raised in Lewiston, went to college at the University of Maine at Farmington, taught special education in Ellsworth, then math in Bangor, earned a master’s degree at UMaine’s Orono campus, joined the choir at St. Mary’s Catholic Church, and is busy and happy and content.

But bring up singing and the mood shifts and the life story becomes less a history than a game board of moving from one singing gig to the next. He sang at church as a boy, played Connie Francis and Perry Como on the stereo, joined choruses as an adult, and then came that Big Audition, the one that opened his voice and his life to Gilbert and Sullivan.

“The desire was there, but my beliefs about myself – well, I just didn’t have the guts to get up on that stage and perform,” said Dube, 42. “Then I was cast and there was the first rehearsal and – oh my God – I was lost. But then, the second week, the music grabbed me. And here we are. This is my 19th year and I have never repeated a role.”

Nor has he ever seen himself in a role. Whether guided by superstition, inhibition or fear, Dube refuses to watch taped recordings of his performances. He also has been known to pace backstage, running his lines nervously before showing up in the spotlight.

“He concentrates very hard but he also has a spirit of fun,” said Monique Gibouleau, who plays Mad Margaret opposite Dube’s Despard in “Ruddigore.” “I know if I had a disaster in one of our scenes, Roland would find a way to cover it.”

That is exactly what happened at a performance last weekend, when Gibouleau had broken her toe onstage and was afraid of slipping in a pool of water left behind from a backstage machine but still had a song to sing in Act 1. Gibouleau ended up having to sit buttressingly in Dube’s lap – and he worked the scene – in which it appeared as if Gibouleau was crushing his leg – for every available laugh without ever stealing from his partner’s lines.

“To me, there’s something very sexy and charismatic when Roland gets into the theater mode,” said Gibouleau, who lives in Bangor and also played opposite Dube in “The Pirates of Penzance.” “People who know him as ‘fifth-grade math teacher Roland’ get a kick out of me saying that. He’s a quiet, mild math teacher by day, and, personally I think, a dashingly handsome onstage evildoer by night. For Roland, it must be really fun to live out a life he would never lead. It’s a privilege to work with him because he’s fun and talented and I maintain: very dashing.”

For Dube, the split in personality is directly related to venue.

“I will go onstage and act the fool in front of anyone,” he said. “But that’s because there’s a script and the notes for the music are in my range. When I am at church, it’s Roland Dube. It’s me. It’s not a character.”

And if you ask what he gets out of the various theater experiences, he will answer quickly, with high eyebrows and a forceful voice: “Exhausted.”

But then he may settle into a more pensive place.

“The applause and laughter from the audience are nice,” said Dube. “But I hope what that means is that the audience is having a great time. I want people to enjoy my performance. I want to make that connection. I wonder why I do this, too. You work and work and work, and then you perform. And then I know exactly why I am doing this. I hear the laughter. I hear the applause. And I know I’ve made the connection.”

Then there is another pause followed by a big, toothy smile beneath a black moustache and, “It’s never dull.”

The Gilbert and Sullivan Society of Hancock County will present “Ruddigore, or the Witch’s Curse” 7 p.m. Feb. 8 and 9, and 2 p.m. Feb. 10 at The Grand Auditorium in Ellsworth. For information, call 667-9500.