Ah, yes, fire, and there tend to be flammable items in the garage.
That is another benefit of the rockwool.
When I was reading about insulating garage doors, someone wrote that an insulated garage door would never be as good as a wall, and if you were converting a garage into living space, it would be more efficient to replace the garage door with a wall.
According to
Cost to Install Drywall - 2013 Cost Calculator (ZipCode based), drywall to cover 33.5 linear feet (268 square feet) would be $102.08 - 119.60, supplies would cost $39.80 - 43.10, and it would take 3.3 hours. For insulation, I would need two
Owens Corning EcoTouch Kraft 3-1/2 in. x 15-1/4 in. x 93 in. R-13 Batts in Bags Insulation-BF12 at The Home Depot $56.74 each.
To use Roxul Comfortbatt, I would need to special order through Lowe's (my parents have a Home Depot card that gives them a 5% rebate\discount). It is $48.63 for half as much, so instead of costing $113.48, it would be $194.52, although it would have a slightly higher r-value.