Speaking at a press conference in France, the 41-year-old said all terms have been agreed and the move is expected to be completed within hours, despite paperwork not yet being signed. Rosenior explained he felt it was important to address the media in person before leaving Strasbourg.
Chelsea are replacing Enzo Maresca, who departed on New Year's Day, and Rosenior could take charge as early as Saturday's FA Cup third-round tie away to Charlton Athletic. The Blues are currently fifth in the Premier League and were held to a 1-1 draw by Manchester City at the weekend under caretaker boss Calum McFarlane.
Rosenior leaves Strasbourg after an 18-month spell in which he guided the club to seventh in Ligue 1 last season and secured European football for the first time in eight years. They are again seventh domestically and top of their Conference League group, although his final match ended in a 1-1 draw at Nice.
"The last 18 months have been the best of my professional career," Rosenior said. "I will love this club forever, but there are some opportunities you simply cannot turn down."
Strasbourg and Chelsea are both owned by the BlueCo group, which facilitated discussions. Rosenior also confirmed that several members of his backroom staff, including Kalifa Cisse and Justin Walker, will join him in west London.
Despite never managing in the Premier League, Rosenior insisted he is ready for the challenge, adding: "I would not have accepted the Chelsea job if I did not believe I was prepared."
Crystal Palace manager Oliver Glasner has confirmed the club would consider selling captain Marc Guehi during the January transfer window if their valuation is met, with Manchester City weighing up a move for the England defender.
Enzo Maresca has spoken publicly for the first time since leaving Chelsea on New Year's Day, less than six months after guiding the club to Club World Cup success, subtly hinting at tensions with those in charge.
West Ham's slide towards relegation deepened after a dramatic late collapse handed Nottingham Forest a crucial 2–1 victory, decided by a VAR-awarded Morgan Gibbs-White penalty in the closing minutes.
Newcastle head coach Eddie Howe has firmly ruled out any move to Manchester United, reaffirming his contentment at St James' Park despite speculation linking him with the Old Trafford vacancy following Ruben Amorim's departure.
