Trejo is starting at second base and batting ninth for Monday's game against the Phillies.
The Rockies selected Trejo's contract from Triple-A Albuquerque on Thursday.
Rockies manager Bud Black announced Tuesday that Trejo made the Opening Day roster, Thomas Harding of MLB.com reports.
The Rockies sent Trejo outright to Triple-A Albuquerque on Friday.
Colorado recalled Trejo from Triple-A Albuquerque on Tuesday.
The Rockies optioned Trejo to Triple-A Albuquerque on Sunday.
Trejo is out of the lineup for Sunday's game against the Mets, Patrick Lyons of TheDNVR.com reports.
Trejo went 1-for-2 with an RBI and a steal in Thursday's victory over Miami.
Trejo went 2-for-4 with an RBI and a steal in Wednesday's win over Pittsburgh.
Trejo remains on the bench for Saturday's game against the Mets, Patrick Saunders of The Denver Post reports.