1) Rockwool and fiberglass are both utterly inert materials [basically sand] - getting all worked up and pretending they are harzardous materilas is a waste of time... more fun to worry about Aluminium cookware IMO. The stuff is very scratchy, and long sleeves are definately reccomended... full hazmat suits are not a benefit to the process [unless you think they are sexy]. Paying attention to this advice may save you some discomfort, but it may also waste an absurd amount of time and trouble... use you common sense. If these materials were not safe, all construction sites would be hazardous waste zones, and all modern buildings would need to be unihabitable.
I would agree that in itself, Rockwool (and fibreglass) is an 'inert material' that presents no long term threat if left undisturbed.
However, while handling this material there can be no doubt that very small fibres are released into the air, and if breathed in they can enter and settle in the lungs. It is the body's reaction in efforts to remove these 'alien' fibres where the problem starts -- but often not until years afterwards.
When working with any dusty material, common sense decrees that wearing a face mask is a sensible precaution. The earlier suggestion to help reduce the volatility of fibres by spraying a light glue mix on the panels may also help, and certainly can't harm.
Yes, it adds marginally to the overall time and expense, but it's not significant to the overall project of constructing panels, and the peace of mind justifies it as far as I'm concerned.
And likewise, if you find the dust irritates the skin, a disposable paper boiler suit will save many hours of discomfort and scratching for anyone susceptible, and costs only a few pence.
Technical Editor, Sound On Sound