The exits, apparently unrelated, have led B-M to bring in Tessa Hopkins - a former B-M healthcare chief - to provide interim, part-time support.
Rockliffe, who was appointed joint head alongside Amie Malkin last year (PRWeek, 27 May 2005), will leave in late October to start his own business.
Sarewitz, whom PRWeek was unable to reach for comment, will leave next week.
The past few weeks have been tumultuous for B-M's London health team: director Monica Shuman left last month (PRWeek, 11 Aug), while the previous month director Sam Barnes defected for Weber Shandwick (PRWeek, 14 July).
The agency has been quick to plug holes, with Athena Medical PR associate director Anna Gray (PRWeek, 11 Aug) and Solaris joint MD Rachel Terry recently joining in director roles (PRWeek, 23 June). Another senior individual, whose identity is under wraps, is also set to join within weeks.
Hopkins, who will work closely with Malkin for at least three months, has spent the past decade at media training and crisis comms outfit Lions Den Communications. She will continue in this role, but her commitments will be scaled back during her B-M secondment.
In May she completed a similar interim director job at Athena (she continues to provide advice to Athena's client, Idis).
B-M's interim London CEO Jonathan Jordan said: ‘We are very much looking to recruit senior healthcare leadership.'
Rockliffe, whose pedigree is in med ed, joined B-M three years ago. His new venture will be health-related, but will be neither a PR nor med ed consultancy. Further details are expected towards the year's end.