Betsy Roberts, head of the private placement group at Hartford Investment Management Co., retired recently. Reached at her home in Connecticut, she said she took time off to be with her family. Curt Nyman, v.p., is serving as interim head of the private placement team, but a search is well under way for a permanent successor, says Cynthia Michener, a spokeswoman with the buy-side firm. Nyman, who joined Himco in 1997, reports to Tim Corbett, managing director. Nyman was on holiday and could not be reached. As of June 30, Himco had $80 billion in assets under management, including $2.3 billion in private placement securities.