Leake and Rondon become eligible for free agency, and Guerra for salary arbitration in February.
The 32-year-old Leake went 3-3 with a 4.35 ERA in 10 starts for the D-backs in 2019 after being traded from the Mariners. He opted out of the 2020 season because of concerns with the coronavirus.
His contract included an $18 million club option for 2021 with a $5 million buyout.
Rondon, 32, had a disappointing season in 2020, finishing with a 7.65 ERA in 23 appearances. The reliever gets a $500,000 buyout instead of next year's $4 million salary.
Guerra, 35, pitched well in 2020 with a 3.04 ERA in 25 appearances. He receives a $100,000 buyout instead of a $3.5 million salary. The team faces a Dec. 2 deadline to offer contracts to Guerra and other unsigned players on its 40-man roster.
The Diamondbacks are trying to rework their roster after finishing 25-35. They traded several of their key players at midseason, including outfielder Starling Marte, left-handed pitcher Robbie Ray and right-handed closer Archie Bradley.