Ventura will move from his role as executive vice president of auction sales, a position he held for a decade, to executive VP of strategy and innovation.
He joined De Beers in 1989 and pioneered the diamond industry's first successful physical spot sale of rough diamonds using online auctions.
Rowley will change from being executive VP of global sightholder sales to executive VP of diamond trading.
He joined the company in 1983 as a trainee diamond sorter and worked in Kimberley, South Africa, and London before being appointed executive director at the Diamond Trading Company in 2007 and then executive VP of global sightholder sales in 2014.
Berridge has left her position as Anglo American lead legal counsel for M&A to become De Beers' executive VP of commercial and partnerships, a new role created to manage commercial ventures and partnerships, including joint ventures with the governments of Namibia and Botswana.
She previously worked at De Beers general counsel from 2008 to 2013 and was a partner at law firm Webber Wentzel.