Castro has made the Rockies' Opening Day roster, Nick Groke of The Denver Post reports.
Castro was previously on the bubble, but after posting a 3.38 ERA and 0.75 WHIP this spring, the Rockies decided he was worthy of a roster spot. The 21-year-old is a power pitcher with a fastball that typically sits in the mid-to-upper 90s, and while Jake McGee has the closer spot locked down, Castro could still have some value as a reliever, especially after boasting an impressive 9.2 K/9 in 18 games at the major league level in 2015.