This is the wording on one of the abilities of the Starseer CURSE OF FATES Curse of Fates has a casting value of 4. If successfully cast, pick a unit within 20". Once per phase until your next hero phase, you can increase or decrease the result of a single dice roll for that unit by one. The wording I want to discuss is "a single dice roll". What does "dice roll" entail? If I cast 6 dice, can I reroll all 6 of them? Or only one of them? Usually when it's only one dice it says so. For example "any single dice". This is the first and possibly first wording that specifically says "dice roll" that I've encountered in the seraphon warscroll list.
Just one dice. It can be yours or your opponents, it can ve the dice between turns, but it is just one dice, not the array of dice.