Notice that I didn't recommend that anyone roast them in hell. My remarks were a prediction, not a recommendation.
Whether Satan is purely symbolic as the embodiment of evil, or whether, as some hold, it is an actual creature, doesn't matter. Those who devote themselves to evil will themselves suffer, and they cannot expect mercy from evil (or Satan).
In other words: "Evil is the ultimate stupidity."
These terrorists, who have devoted their lives to evil--to Satan--are extremely stupid.