How to modify the initial orientation (and position) of a robot model

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I have a urdf model of a robot that I inherited. I've built a ROS package around it. When I load it into Gazebo, it ends up being below the floor place, so it "hangs" underneath the floor due to the collision detection on the feet not allowing them to fall through the floor. The rest of the robot is invisible under the floor unless I make everything transparent.

I've tried changing the origin of the parent node of the URDF model, and I've also tried passing (x, y, z, r, p, y) parameters in the args list in the launch file. Neither one seems to change the behavior in any way.

How do you specify an initial orientation and position for a model?