When you are a rebuilding team, so much of the season is spent on young talent. You want to focus on if your talent is developing, do you have any potential stars, or do you need to move someone to make room for another prospect. Little time is spent on adding free agents to the roster, as most of the time this creates sort of a logjam if you will and can block some prospects. That is not the case, however, with minor league signings. These are low risk and if they pop, great, you have a solid player on such a low financial cost that it is a plus. If the player doesn't pop, then you have depth, or can get out of the create at a minimal financial loss.
The Rockies have added some veteran depth this offseason, but they should not be done. A lot of this season should be about letting some prospects play and develop, but you have to build your depth out and some of that needs to be done in the upper minor leagues or potential major league players. The Rockies will most certainly let a lot of their young talent prove themselves but taking a shot on these three players as minor-league invitees, could prove valuable for the long season.