Conan Hero Book, p.5 wrote:
To perform the Melee Attack action, the hero chooses one enemy in their area...to attack and assigns one or more gems from their Reserve zone to their Melee Attack space. The hero may choose one of their equipment cards that has a Melee Attack bonus to attack with. (At this point choose to Sacrifice or not) Then, for each gem assigned, the hero rolls one die of the type indicated...
This is my reading and fulfils the 'before the dice are rolled' part of the skill.
The ranged attack is similarly worded (in English).
Is the skill worded differently in French?