Why wouldn't you put them IN the truck?
Fishing POLES get strapped to the roof. Fishing RODS go inside the truck. If you have to ask the difference then you have poles.
Place the butt of the rods by the passengers feet. Tips go back toward the middle of the rear seat.
If you just simply can't put them inside the truck then do this.
Go to your hardware store and get a length of 4" PVC, a cap, a slip to threaded adapter, and a screw in plug. Make yourself a rod tube and strap that to your roof. Put the rods in a rod sock before placing them in the tube though.