Rosenberg was drafted by Tampa Bay in the eighth round out of Cal State-Northridge in 2016. The left-handed reliever split the 2021 season between three teams, mostly with the Triple-A champion Durham Bulls where he went 4-0 with a 2.35 ERA and a 35-percent strikeout rate. In December, the Los Angeles Angels selected him in the Rule 5 draft. He opened the 2022 season at Triple-A Salt Lake where he appeared in just one game before being recalled by the Angels on April 18. He made his major-league debut that night by pitching one inning against the Houston Astros.
In his sophomore season at Cal State-Northridge, Kenny led the Big West Conference pitchers with 118 strikeouts.