Kelley Millet, senior managing director and head of investment-grade capital markets and syndicate at Bear Stearns, has added trading and research to his investment-grade managerial responsibilities, according to senior firm officials. Millet declined comment. Harry Rosenberg, the former research and trading head who left the firm last week, also oversaw high-yield trading and research. It could not be determined who, if anyone, has replaced him in that capacity.