Mr Alexander's role will replace three positions at the James Packer-controlled gambling giant: chairman, executive deputy chairman and chief executive.
Crown said on Thursday that it will have a simpler organizational structure after Mr Craigie's departure on February 28, reflecting its decision to focus more on its Australian assets.
Mr Craigie's departure follows major changes in strategy at Crown: the company has dropped plans to demerge its international business, sold down its stake in the Melco Crown Entertainment casinos joint-venture in Macau, and dumped a new Las Vegas casino plan, while also dealing with the detention of 15 Crown employees in China in October.
"Given the recent decision to reduce Crown's investment in Melco Crown Entertainment and to discontinue the proposed Las Vegas project, the board has decided that following the cessation of Mr Craigie's employment, a simplified organisation structure reflecting the changed focus of Crown's business should be adopted," Crown said on Thursday.
Mr Alexander said Mr Craigie had been a key executive for more than 20 years played a major role in building Crown Resorts in Australia.
"In particular, Rowen has ensured Crown Melbourne has remained the largest and most successful integrated resort in Australia, with the highest standards of social responsibility," Mr Alexander said.
"Rowen has also played a major role in Crown's expansion in Perth, Macau and in the award of a new licence in Sydney."
Mr Craigie joined Crown's Melbourne casino in 1993 and was appointed chief executive and managing director of Crown Resorts in 2007.
In a statement, Mr Craigie said he was proud of his contribution to building up Crown from a single casino in Melbourne.
"In particular, I have been fortunate to have worked closely with three remarkable Australian entrepreneurs in Lloyd Williams, Kerry Packer and James Packer," Mr Craigie said.
Mr Craigie will work as a consultant with Crown on specific projects.