Unable to rotate ground_plane

edit

I believe this is a bug in Gazebo regarding the way planes are specified. A way around it for now is to set the normal vector as well as the pose. So for your example, the model will be:

<model name='ground_plane'>
  <static>1</static>
  <pose>0 0 0 0 0.2 0</pose>
  <link name='link'>
    <collision name='collision'>
      <geometry>
        <plane>
          <normal>0.199 0 0.98</normal>
          <size>100 100</size>
        </plane>
      </geometry>
    </collision>
    <visual name='visual'>
      <geometry>
        <plane>
          <normal>0.199 0 0.98</normal>
          <size>100 100</size>
        </plane>
      </geometry>
    </visual>
  </link>
</model>