Dr Ewell, who is currently executive director of the Theological Commission of the World Evangelical Alliance (WEA), will start the role in September.
Bishop of Leicester Rt Rev Martyn Snow, the chair of trustees at Redcliffe College said: "I give thanks to God for calling Rosalee to this significant role.
"Redcliffe has been through some big changes in the last couple of years and Rosalee has been a part of that journey. Now she will lead Redcliffe as we deliver flexible mission training around the world.
"Her considerable reputation as an academic who is deeply committed to partnering with God in both local and global mission is a huge asset and I look forward to seeing how God uses her in this role."
Dr Ewell will stand down from the board of Redcliffe College - where she has served as a trustee for three years - to start her new position.
Born and raised in Brazil, she has previously worked at the South American Theological Seminary and at the Langham Partnership's project Latin American Bible Commentary.
Current principal Rob Hay is stepping down at the end of July to start a new position at the Diocese of Leicester.
An interdenominational, evangelical and international college, Redcliffe says it specialises in cross-cultural mission, leadership and linguistics, translation and literacy.