You do not need a roof. There are 360 3D theaters such as the Bubble Show at City of Dreams casino in Macau or TurtleTrek at SeaWorld Orlando. What I think @Turtle may not realize is that the tour trams are not moving forward during Kong Kong 360.
Turtle Trek isn't the same system as Kong 360. There's nothing above riders on Kong. It's just a curved screen on each side of the tram. And I'm sure you could have a moving attraction that utilizes this system, but there'd be no point to it unless it's only one scene/aspect of the overall attraction.