Freeman, 26, has spent parts of the last two seasons with the Cardinals, appearing in 37 games (1-2, 4.18 ERA). He was 0-1 with a 3.78 ERA (16 2-3 innings) in 13 games for Memphis, though he had allowed just two earned runs over his last 10 appearances.
Rondon, also 26, will be looking to make his Major League debut after spending the past eight seasons in the minors. He was 1-0 with a 2.51 ERA (14 1-3 innings) in 11 games at Memphis.
The Cardinals optioned reliever Eric Fornataro to Memphis and placed Tyler Lyons on the 15-day disabled list with a left shoulder strain. Lyons started Monday's game with the Chicago Cubs and allowed seven runs in two innings.