My launch field is two hours north of my house. Transporting large rockets to that field is difficult because they do not fit into the SUV very well, especially if I am also trying to transport people to the launch. After the launch the rockets tend to smell like burned rocket fuel, black powder, and sulfer. Passengers don't really like that very much.
The solution was to get the rockets out of the car and put them on the roof. This eliminated the need to break them down for transport and it makes the inside of the car smell better on the drive back home. Rockets are by nature aerodynamic and mounting them on the roof has the added effect of intimidating other drivers.
My rocket racks are modified ski attachments that can hold airframes up to five inches in diameter. I attach them to the luggage rack when going to a launch and remove them afterward. They are easy to mount, easy to load with rockets, and are secure enough that I've never had a rocket fly away while driving.