If you go to the Rockies original roster in the game, it is a bit different than the one that the team fielded later in the season or even on Opening Day.
Charles Johnson is listed as starting catcher on the original roster but by the time spring training ended in 2005, the Rockies traded him to Boston for pitcher Byung-hyun Kim (of 2001 World Series fame). The Red Sox later flipped Johnson to Tampa.
The Rockies also made a few transactions in the first few weeks of the season, including signing veteran reliever Jay Witasick, trading outfielder Reggie Taylor to Tampa for reliever Bobby Seay, trading pitcher Allan Simpson to Cincinnati for Jose Acevedo, and reliever Javier Lopez (later of Giants World Series fame) and Alfredo Amezaga were claimed off waiver by the D’Backs and Pirates.
Catcher Danny Ardoin (who started the majority of the games at catcher for the Rockies in 2005) is not in the game. Nor is Opening Day starting third baseman Jeff Baker (because Opening Day was his MLB debut), outfielder Cory Sullivan, or relievers Marcos Carvajal and David Cortes, both of whom logged more than 50 innings out of the Rockies bullpen.