Flight orientation in simulation using ROS

Hello all
I am trying to fly a quadcopter to different waypoints using a PX4 SITL in Gazebo simulation.
My issue is that I don’t know how to orientate the drone when it flies. It always is oriented on the positive x-axis. An example video can be seen here: flight video

A simplified version of my code is shown below:

ros::Publisher local_pos_pub = nh.advertise<geometry_msgs::PoseStamped> ("mavros/setpoint_position/local", 10);
Vector3f vect  (0.0f,  0.0f, 2.0f);
geometry_msgs::PoseStamped msg;
msg.pose.position.x = vect(0);
msg.pose.position.y = vect(1);
msg.pose.position.z = vect(2);

Should I also fill the quaternion (present in the Pose message: doc) of the message? Or is there a better way to do that?

Thank you for any help!