After spawning the robot in Gazebo, the TF tree is disconnected like this. This is because Gazebo is not publishing the moving joint states to /tf. A partial fix is here which correctly sets the parameters of the diff_drive plugin and connects the left and right wheels to the tf tree like this. The center wheel is still disconnected, it seems to require the Gazebo joint state publisher plugin, which I'm trying to get to work.
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