Sam says he has an idea of where the roster is located and sends you to a gorge. When you get there, follow the markers, making sure you don't perform any aggressive act as to cause the mercenaries to come after you. Each area is connected by a zipline, so to get from one part to the next, find the zipline and then use it.
When you get to the area where you must climb a lot of stairs and arrive at the top, take out your camera and zoom in on the bridge in the distance. You must take a picture of the meeting and once it succeeds, you will have 50 seconds to find a RPG and use it to stop the pirates from leaving. Take the zipline down and grab the RPG not too far from where you land. Aim at the vehicle on the left and fire, hopefully destroying it on the first shot.
Note that once you fire the RPG for the first time, all of the mercenaries in the area will become hostile and come after you. Your first objective should be to take out the other vehicle on the bridge, then worry about the enemies coming from behind. Now, you need to go from area to area like before with the ziplines, but you will be fighting enemies along the way.
When you finally make it to the area right before the bridge, take out the rest of the enemies and heal up if you need it. As soon as you grab the roster from the dead body, enemies will pour in from behind and from the front. Jump over the side of the bridge, deploy your Wingsuit and Parachute to make it to the marker, where the mission will end.
