Are you sure it is rockwool or has someone just used a generic name (how many people use a real Biro or Hoover but most people use the name)? Rockwool is safe but, going back 50 years it may have been, say, fibreglass. Nevertheless, taking waterboatman's advice should be fine - it's what I did when I icreased the thickness of insulation in our loft. Without the face mask etc you are likely to end up itching for a day or two and, perhaps, an irritated throat as well.