This achievement is a pain, so let me give a few pointers for those of you attempting this.
1) The rocket moves you exactly 10 spaces forward.
2) Yes, this must be done with a single use of the item. You have to have all 3 opponents skewered at the same time.
3) The tile you are currently on and the tile you land on at the end of the rocket ride are safe spaces where the opponents can't be skewered. This means that you actually need to have all 3 opponents within NINE spaces of you, since the last one won't count.
Now for the hard part, actually getting all of your opponents lined up, with you in last place. Unfortunately, as this is a purely luck-based dice game, a lot of it is down to luck. In attempting this and the triple eggplant achievement, I came up with two possible strategies.
Strategy one is just to play the game normally and try to use portals and/or killing opponents to get them all together in roughly the same spot, with you in the back. This is far more enjoyable, but takes a lot longer (this is how I got the rocket achievement).
Option 2 is to start a new game, win the first mini-game and hope you win a rocket (if you don't, quit and restart), hope you're in last place after this turn (if you aren't, quit and restart), win the next mini-game so you get to go first, and then skewer away. This will likely be faster overall, but will be incredibly tedious with how much you'll be restarting. Pick your poison, and good luck!