It was established in 1917 as Odd by 12 boys, and played local friendlies, became it was not permitted to join the Football Association of Norway (NFF).
During the early 1920s, the number of clubs joining NFF increased rapidly, and by 1923 Odd only played a single match during the entire season.
[5] Trygve Falstad and Richard Olsen became the team's most important players, and at the same time started negotiating the right to join NFF.
Rosenborg was located in a labor neighborhood, but had chosen to join NFF instead of the Workers' Federation of Sports (AIF).
With the rising class awareness of the mid-1930s, socialist politicians and unionists encouraged people to take sides by instead joining worker sports clubs.
The goal was initially to establish a good training possibility for the players during the winter, when the city's football grounds were covered by ice and snow.
The initiative was taken by Harald Petersen, Olav Fossum and Trygve Falstad, who were worried that the football team would again lose matches because they were outrun by the opponents.
The teams were named Niffs and Fiffico, and results were announced on public places through cryptic poems not understandable by German soldiers.
Rosenborg held training at local pitches, and would sometimes take day or week trips around Trøndelag to play friendly matches, often without or with fake travel permits.
[8] In 1948, Harald Petersen resigned as president, after having held the position on and off since 1923, after NFF had excluded him after a professional boxer he had been manager for had played a match during the sports strike in 1941.
[29] In the 1955 Cup, the team reached the round of 16, where it lost marginally 4–2 against Larvik Turn, double-reigning Main League champions.
[32] John Krogh made his debut for Rosenborg that season, and also became the club's first player to play for the Norway national football team during 1962.
[44] The forward duo were instrumental in Rosenborg's winning the 1967 First Division; other important players were Nils Arne Eggen, Jan Christiansen, Svein Haagenrud.
He broke with Rosenborg's tradition of playing offensive and entertaining football, and instead introduced a more rigid defensive strategy, with the wings often functioning as extra side backs.
[54] In the UEFA Cup, the team advanced past IFK Helsinki, and lost to Belgium's Lierse on the away goals rule.
[58] Curtis had in the meantime become manager of the Norway national football team, a job he had held until mid-1974, when he was severely injured in a car accident, where his girlfriend was killed.
[63] The season saw the break-through of three young players—Øivind Husby, Ola By Rise and Knut Torbjørn Eggen—and ended with Rosenborg winning the league and being promoted[64] and Eggen becoming top scorer.
Eggen concluded that while the team had many good individual players, they lacked sufficient cooperative coordination, which would later be the essence of his philosophy.
Cavanagh had been coach for Manchester United, where he had done an excellent job at exactly that, but lacked abilities in team selection, tactics and inspiration.
[73] Forward Arne Dokken transferred from Panathinaikos and local talent defender Rune Bratseth was signed.
Dokken led the team to an eighth place in the league, and a victory over Linfield and loss for Red Star Belgrade in the European Cup.
[29][47] The cup final was dominated by Rosenborg's reserve goalkeeper, Frode Olsen, who had been lent out to opponent Strømsgodset for the season.
[87][88] Rosenborg signed the defender Stig Inge Bjørnebye, the midfielder Øyvind Leonhardsen and forward Tore André Dahlum.
[95] The 1994 season saw the return of the loaned-out players which would become central on the team: forward Harald Martin Brattbakk and midfielder Roar Strand.
[29][47] Because only all-seater stadiums were to be allowed for UEFA matches from 1997, Rosenborg needed to expand Lerkendal, or face a limit of 2,800 spectators per game.
[100] In the group stage, Rosenborg beat IFK Göteborg, at the time regarded as Scandinavia's best football club,[101] in both matches, but failed to collect points against Porto.
That year Rosenborg had the highest average player age in Champions League and was the only team to have played seven consecutive seasons in the group stage.
[117] In the Champions League group with Inter, Lyon and Ajax, Rosenborg failed to win a single victory, but managed four draws.
However, Rosenborg failed to beat Deportivo de La Coruña in the Champions League qualification, and instead played in the UEFA Cup.
[138] By July, Høgmo was burned out—in part because of pressure from journalist caused by mediocre results and constant changes to the positions—and Tørum took over as acting manager.