Bio
Julio Rosario comes to Sioux City after three seasons with the Kansas City Royals organization. Rosario was signed by Kansas City on November 21, 2022, as an international free agent and was sent to his native Dominican Republic for his professional debut in 2023. The right-hander reached class A Columbia in the Carolina League in 2025. He would appear in 30 games in relief with five saves and a 4.35 ERA in 49.2 innings. Rosario struck out 51 and posted a 1.289 WHIP for the season. He was particularly solid in the month of May, allowing just two earned runs in 13 innings and for the month of June, pitching another 13 innings, he surrendered four earned runs.
In 2024 Rosario started the season in the pen for the Royals club in the rookie-level Arizona Complex League. He went 4-2 with a 2.45 ERA with three saves over 29.1 innings. He struck out 40 while leading the team in games pitched and in saves, and finishing second in strikeouts. Rosario began the season working 10 scoreless innings over four appearances, and he closed out the last full month of the season yielding one earned run in 11 innings in August.
Rosario would earn a shot at A-level Columbia in August of 2024 and would go 2-0 in seven games with a 2.40 ERA. Rosario would punch out 16 in 15 innings with a 1.200 WHIP for Columbia. He picked up his first win for Columbia, tossing three scoreless relief innings on August 8 against Kannapolis (Chicago White Sox).
Rosario would go 1-4 with a 3.18 ERA in 2023 in 12 games making three starts with the Royals Blue of the Dominican Summer League. The right-hander allowed more than one run only twice in 12 games and walked just three over his final 15.1 innings to go along with six walks all season in 28.1 innings. For his career, the right-hander is 9-13 with a 3.38 ERA in 122.1 professional innings with 127 strikeouts and a 1.234 WHIP. Rosario, 23, hails from Azua, Dominican Republic.