Despite winning five races with Lorenzo, and helping the Spaniard to second in this year's MotoGP World Championship, Romagnoli wanted a return to a more hands-on role for 2010.
"I'm very happy that Daniele Romagnoli has agreed to join us,” commented Poncharal. “He has a top profile but more importantly he brings a lot of technical expertise and experience with him. I've no doubt that he will be a huge asset and his input will be vital in helping us develop the new bike."
Gary Reynders - who recently worked as crew chief for Colin Edwards (2008) and James Toseland (2009) at Tech 3's Yamaha MotoGP team - will become Takahashi's crew chief.
Ben Spies, who has replaced Toseland, is bringing his own crew chief Tom Houseworth to the MotoGP part of the Tech 3 operation.
The Tech 3 team will debut its new Moto2 contender with de Rosa in Valencia at a two-day test on December 9-10. Takahashi is due to embark on a rigorous winter training regime before making his debut in early 2010.