White was ranked the second-best graduate transfer in the 2020 class, according to ESPN. His move was first reported by Jeff Goodman of Stadium.
"(White) was a guy who I anticipated being back," ASU head coach Bobby Hurley said in a May 6 Zoom teleconference with reporters. "I was a little bit blindsided by his departure."
The newest Rebel will immediately be eligible to play in 2020-21 as a graduate transfer for his final season.
"We are extremely excited to welcome Romello to the Ole Miss family," Ole Miss head coach Kermit Davis said in the school's announcement. "Romello is a very accomplished player that impacted winning at a high level at Arizona State ... He has such a high ceiling in front of him that can impact the SEC in a great way."
Former ASU men's basketball assistant Levi Watkins, who was on Bobby Hurley's staff during White's redshirt freshman season, is currently on the Ole Miss coaching staff in a similar role.
Friday does not mark the first time White has committed to a school in the Southeast, or even in the SEC. According to 247Sports, White originally committed to Tennessee in 2015 before de-committing, committing to and signing with Georgia Tech.
After being released from his National Letter of Intent with Georgia Tech in May 2016, the 6-foot-8 forward committed and signed with ASU.
The Atlanta, Georgia native moves roughly 1,510 miles closer to home in the move from Tempe, Arizona to Oxford, Mississippi.