After landing as a staff writer on the final season of Da Ali G Show, for which he and the staff received an Emmy nomination, Rogen was guided by Apatow toward a film career. Rogen was cast in a major supporting role, and credited as a co-producer, in Apatow’s directorial debut The 40 Year-Old Virgin. After receiving many good notices for that performance, Universal Pictures agreed to cast Rogen as the lead in Apatow’s next directorial feature, Knocked Up.

Rogen has appeared in the films Donnie Darko, You, Me, and Dupree and Fanboys, in addition to the Apatow-produced comedies Anchorman: The Legend of Ron Burgundy and Superbad (a semi-autobiographical comedy Rogen originally intended to headline years ago, co-written by Rogen and Evan Goldberg). Rogen also wrote the screenplay for another comedy which Apatow helped co-produce, Owen Wilson's Drillbit Taylor.

Rogen was born in Vancouver, British Columbia, Canada, the son of Mark Rogen, an assistant director of a Workmen's Circle, and Sandy, a social worker. He had a Jewish upbringing and attended Camp Miriam, a Habonim Dror camp where he would perform stand-up comedy for fellow campers. Rogen got his start in show business at age thirteen after signing up for a comedy class. With his trademark deadpan humour, he went on to win the Vancouver Amateur Comedy Contest at sixteen, then headed south of the border to continue stand-up and acting.

Rogen's first exposure to the entertainment field began with commercial work in Canada at the age of thirteen. After trying his hand as a teenage standup comic, Rogen snapped up his first starring role in the Judd Apatow/Paul Feig 1980s-set teen series Freaks and Geeks (1999-2000) with only two auditions. He played cynical, acerbic "freak" Ken Miller. Apatow was very impressed with Rogen's improvisational skills, believing that the young actor was just as talented as many comedy writers. After the show was cancelled in the middle of its first season, Rogen was cast in a similar role in Apatow's second, also short-lived series, Undeclared (2001-2002), and went on to write several episodes. In 2001, Rogen also had minor roles in Donnie Darko (playing Ricky Danforth), which he did not initially understand during its filming and Dawson's Creek, in an episode he claims he never saw. Following the cancellation of his second series in 2002, Rogen developed a soured attitude toward television, not wanting to act on another show unless Apatow was involved.

Rogen's first writing job came when Apatow invited him to create some ideas for Undeclared, being hired for writing before being offered an acting role. Rogen and most of the writing staff had not worked on a half-hour sitcom before, forcing them to learn as they went along. During the show's run, Rogen wrote one episode by himself and co-wrote four others.

Rogen and writing partner Evan Goldberg joined the writing staff of Da Ali G Show for its second season. In 2005, Rogen, Goldberg and the Ali G Show writing staff received a Primetime Emmy Award nomination in the Writing For A Variety, Music Or Comedy Program category. Rogen and Goldberg were on the staff for what became the final season of that program. However, unlike Rogen's previous television experiences, this series was not cancelled by its network. Rogen stated that during each season, the show's interview subjects would become increasingly aware that they were being pranked, making it difficult to keep producing the series. Rogen credits much of his success to his second Cousin Oliver Davies, who pushed him through the tough times and left him always wanting more. The famous "you're gay" scene from the Forty-Year-Old Virgin was written by Davies, and Rogen credits much of his comedic style to his hilarious cousin. In a recent interview with Tokion Magazine, Rogen admitted to having made uncredited contributions to Cohen's film version of Borat.[citation needed]

Among his many upcoming projects, Rogen will co-star in the 2007 comedy, Superbad, which he had written years ago as a starring vehicle for himself. Looking for what Rogen described as an eighteen year-old version of himself, frequent collaborator Jonah Hill was cast as the lead. Rogen has also written the screenplay for the upcoming Owen Wilson vehicle, Drillbit Taylor, based on a seventy-page scriptment written by John Hughes.[10]

Rogen returned to the big screen in 2005 with a major supporting role in Judd Apatow's directorial debut The 40-Year-Old Virgin. The film was a massive success, grossing $109,449,237 domestically ($177,358,395 worldwide).[11] Citing that film's success as proof that studios can gamble on new stars when the project's premise is strong, Apatow cast his protégé, Rogen, as the lead in the 2007 film Knocked Up.[12] Upon completing The 40 Year-Old Virgin, Apatow had approached Rogen about potential starring roles, but the actor suggested many high concept science fiction ideas. After Apatow insisted that Rogen would work better in real life situations, the two agreed on the accidental pregnancy concept that became Knocked Up.[13]

Spots in Anchorman: The Legend of Ron Burgundy, The 40 Year-Old Virgin, and You, Me and Dupree have also ensured him a minor place in Hollywood's Frat Pack. In USA Today's (who originally coined the "Frat Pack" term) recent profile of the group, they mention those actors' rising salaries makes it financially wiser to cast newcomers like Rogen, citing his roles in Virgin and Dupree as successful examples.[14] When asked in an interview if he is in the group, Rogen has stated he is not sure. In Rogen's starring vehicle, Knocked Up, Frat Pack members (and past co-stars) Steve Carell and Owen Wilson filmed cameos as themselves, being interviewed by the film's female lead, Katherine Heigl.[15]

Rogen and Apatow's latest project, as of summer 2006, is a comedy centered on high school students titled Superbad at Columbia Pictures. Rogen and Evan Goldberg wrote the film, with Apatow as co-producer. Jonah Hill and Michael Cera star as the teen leads named Seth and Evan. While Rogen did pen Owen Wilson's upcoming Drillbit Taylor, he does not expect to appear in it since the script mostly involves high school students. Freaks and Geeks co-star James Franco also revealed that he will reunite with Rogen for the Apatow-written comedy, Pineapple Express.[16]

Though Seth Rogen has penned scripts for both film and television, his comedic stylings tend to rely heavily on improvisational dialogue. Judd Apatow noticed this improvisation talent on the set of Freaks and Geeks, which influenced his decision to have Rogen write for Undeclared and pitch jokes for The 40 Year-Old Virgin. As with most Apatow projects, despite the long process of writing the screenplays and having table reads and rehearsals, the dialogue in Rogen's films is usually not what was on paper.[13] Rogen states his preference for improvised dialogue is because it makes a line not sound scripted, capturing the essence of real friends spouting jokes.[17] Because Apatow never stops rolling after takes, allowing his actors to improvise differently each time, Rogen's two largest film roles to date (The 40 Year-Old Virgin and Knocked Up) both achieved the rare milestone of shooting over a million feet of film, almost unprecedented for comedies.[13]

Rogen moved to Los Angeles at the age of sixteen, after Judd Apatow discovered him in Vancouver. Apatow immediately took a liking to Rogen, finding him to be surprisingly funny at the early age of sixteen. During his late teens, Rogen's parents moved from Canada with him, but by the time he landed his second television series, his parents would live in both Canada and the United States. Rogen still resides in Los Angeles. He continues to write and produce with longtime writing partner, Evan Goldberg, with whom he has worked with on Da Ali G Show, Knocked Up, and Superbad, the latter of which is a semi-autobiographical take on their longtime friendship. Rogen has a girlfriend of two years, with whom he lives.[18] Rogen and his girlfriend, Lauren Miller, attended the film premieres of The 40 Year-Old Virgin and You, Me and Dupree.[19][20]

Rogen has described the shock of being thrust into an industry where he is now working alongside the comedic icons he grew up watching, such as Will Ferrell, Owen Wilson, and Jim Carrey. Rogen cites the Adam Sandler album, They're All Gonna Laugh at You as the funniest thing he has ever heard, stating that the track "At A Medium Pace" was the seed for what became his comedic persona. Rogen was also a huge fan of the Da Ali G Show's first season, so it was a shock to suddenly work for Sacha Baron Cohen, whom Rogen has called a genius in several interviews. Rogen cites the films Porky's and Bachelor Party, in addition to films by Kevin Smith, as inspirations for writing sex comedies. [21]