He will face the Marlins in Miami on March 31. It's the first opening-day assignment for the 32-year-old De La Rosa, who went a career-best 16-6 with a 3.49 ERA last season.
The Rockies made the announcement Wednesday. The move was expected with left-hander Jhoulys Chacin sidelined with a sore throwing shoulder and not expected to be ready for the start of the regular season.
De La Rosa allowed two hits in three scoreless innings in his last spring training start on Tuesday.
His 55 wins with Colorado are the fifth-most in franchise history.
De La Rosa is entering the final year of a four-year contract.