Cut and pasted from the Roxul website:
ROXUL COMFORTBATT[emoji]174[/emoji] is thermal insulation for use in exterior walls, attics and crawlspaces. It provides indoor comfort and energy savings all year ‘round.
ROXUL SAFE’n’SOUND[emoji]174[/emoji] is soundproofing insulation for use in interior walls, ceilings and floors to help create a quieter home.
I'm not sure, but I suspect that means the Comfortbatt has some sort of paper facing as a vapor barrier?
Mineral wool is mineral wool, and once it's inside a smoker, who cares what "brand" it is or is not. If the "non-branded" mineral wool board works out at a lower price to fill the void you need, I would go that route. Either way you want un-faced mineral wool.
Another plus of the board form is it will not want to sag when installed as it's fairly ridged. I have heard of batt mineral wool settling over time inside smokers. I've seen several builds where they welded in "nails" to hold panels in place and prevent this.