You roll all of them. :). Hit and Die by guax and Prosaiko wivh is a skirmish hack of MiniBX also has a very cool alternative (and it is free). I tested 5lvl characters and this works. Thanks so much for asking, hole everything is clear.
Do you roll all of them? So like, when fighting a red dragon, one needs to make an attack that breaks a 10d8+6 defense initial defense?? I always thought you rolled each dice separately for soaking, ao trying to attack a red dragon would be Attack VS 1d8+6 and if it beats the defense the dragon's HD is reduced.