For a modern diesel to roll coal, as it is called around here, it needs to be modified. With factory tuning, diesel engines will not roll coal. A chip upgrade to the tuning will provide a boost in power, at the expense of fuel efficiency.
If I understand correctly, when a diesel engine is rolling coal, it is because it is running excessively rich. This produces a lot of power, but also blows a super dirty exhaust.
In talking to people on the subject, some kids (I say kids, because the majority of those that like to roll coal are in their teens or early twenties) like to roll coal as a show of power. But most like to roll coal just to annoy others.
Somehow, a big truck that rolls coal makes a boy into a man. Or so they think. Personally, I suspect they are trying to overcompensate.