Del Rosario gave up three hits and two runs in 1 2/3 innings in Sunday's loss to the Dodgers and had a 9.00 ERA in four appearances. Carpenter opened the season with the Astros before being sent down May 15 after going 0-2 with a 4.02 ERA in 14 games. He appeared in four games at Oklahoma City.
"They felt he was throwing the ball well enough to be called up, and with Enerio throwing [Sunday] this gives us a full bullpen for today, as well," Astros manager Brad Mills said.
Under a new rule, the Astros were able to add a 26th player to their roster for the doubleheader against the Rockies and added Lyles. The young right-hander showed up at the ballpark hours before Monday's first game before his teammates urged him to go back to the hotel and get more rest in advance of his start.