Of course, he's the 25th man and he'll be sitting behind third baseman/outfielder/part owner/scout/player to be named later/first baseman Casey Blake, but he's on the roster.
Sheldon Ocker says that Wedge will have to creative (oh joy) to get Garko some ABs, maybe even using Pronk in the field:
Getting enough at-bats for Garko to stay sharp might be difficult. At times he will play first against left-handed pitchers, but he might have to share that role with Victor Martinez, who probably will be given a break from catching by playing a few games at first.
Travis Hafner also might play a few games at first (he is considered more proficient than Garko defensively) and leave the designated hitter duties to Garko.
I'm seeing this as a Daniel Gibson type situation, Garko is gonna sit at first but eventually he'll force his way into the lineup.