I just read something on the net that suggests i've been doing this spell wrong, so i'd thought i'd just check. It's great if i am wrong, because the way they're doing the spell is alot better than my way

Soul Stealer says..."the target unit takes three attacks worked out in the usual way. Targets get no armour saving throws"
I assumed "worked out in the usual way" means i roll 3 dice, and any 4+ are hits.
The post i just read suggested those 3 hits are automatic (eg. you don't need to roll)
Which is the correct way please?