The MediaCom associate director, Mark Sherwood, is joining as the strategy director working alongside Danny Stickney, who has been promoted to media director.
Sherwood takes on responsibility for the strategic output for all of Rocket's clients. He leaves MediaCom after four years and was most recently responsible for planning on the Masterfoods account. His most recognised work included a campaign for the Milky Way Lucky Stars brand that won a Campaign Media Award in 2001.
The award, for best use of consumer magazines, linked the Lucky Stars variant with interactive games, exercises and competitions in BBC children's magazines.
Sherwood played an integral role in MediaCom's ultimately successful pitch for the Masterfoods account last year.
Stickney takes on responsibility for the general management of the agency.
He has been at Rocket for four years and will manage contracts, the day-to-day running of the office and relationships with media owners.
He has previously worked at PHD and Media Planning Group and oversees accounts including GWR Group, Adnams and Granada Sky Broadcasting.
Both Sherwood and Stickney will report to Holden, who moves to his new role at PHD next month. Sherwood joins Rocket on 1 September.
Holden said: "Rocket works well when it is run by two people. Getting the partnership right is very important. Stickney's management and Sherwood's creativity will be the perfect formula for taking Rocket forward."
Separately, Rocket has just picked up the strategic communications account for Fashion Box, the owner of the Replay clothing brand.
Replay plans to strengthen its presence in the UK as a sponsor of this year's MTV European Music Awards in Edinburgh. Rocket is planning a campaign to support this sponsorship.