His best season was in 1992, when he posted a 7-1 record in 68 relief appearances. Rojas had an amazing 1.43 ERA in 100.2 innings, and a WHIP of 1.043. He primarily was the set up man for closer John Wetteland (37 saves in 1992), but Rojas was able to accumulate 10 saves that season.[2]
On May 11, 1994, Rojas struck out three batters on nine pitches in the ninth inning of a 4-3 win over the New York Mets. Rojas became the 19th National League pitcher and the 28th pitcher in major-league history to accomplish an immaculate inning.[3]
Mel Rojas joined the Sinon Bulls of the Chinese Professional Baseball League in Taiwan in 2004, played 11 games, posted 3 saves with 1.20 ERA and 14 strikeouts in 15 innings, but then was released by the team after the season ended.[4]