Prior to the 1952 season, the Bears became an affiliate of the Pittsburgh Pirates, and as part of a working agreement between the Braves and the Pirates, Roberts became a member of the Pirates organization for a $10,000 sum. Originally a shortstop in the Negro leagues, he became a second baseman during his tenure with the Bears, and started to build a reputation as an excellent fielder, leading all minor league second basemen in fielding percentage in 1953.
Before the 1952 season, the Chicago Bears became affiliated with the Pittsburgh Pirates, and as part of a collaboration between the Braves and Pirates, Roberts joined the Pirates organization for $10,000. Initially a shortstop in the Negro leagues, he switched to second base during his time with the Bears, and began establishing himself as an outstanding fielder, leading all minor league second basemen in fielding percentage in 1953.