I never understood this thing about normal things being "dangerous". people say it all the time, usually people who have never tried it. i get a lot of weak people who have never done deadlifts tell me deadlifts are bad for the back. if they would shut their mouth and do them for a few weeks they would see that it is the best way to avoid problems with your back by strengthening it. the reason why you can turn your head the way you can is because its not dangerous. you can't turn your head 360 degrees because you will break your spine. notice how the body is designed so brilliantly yet we think we're smarter? notice how the people saying not to use your body are people who aren't extremely strong/healthy

if your neck hurts when you turn it, it means its weak and needs exercise. it amazes me when people do situps and say that their neck hurts so they avoid it. how do i know? i used to have a weak neck.

the best way to strengthen your neck is through wrestler bridges. indian wrestlers have done them for hundreds of years.

lie on your back, and have your feet flat on the floor. elevate yourself so that your head/forehead is resting on the floor, and your back and butt is off the ground, supported by your feet. this will make your legs spine and neck very strong. when you can hold this for 3 minutes you'll never get neck pains or back pains again.

by the way if you are doing neck "rolls" as you call them, don't do them the way i see other doing them. do them very slowly, because most of us probably don't have necks used to moving alot therefore the muscles holding them are very tense. moving your body rapidly while tensing against the force IS a good way to injure yourself (this is not the body's bad design, it is a result of our ignorance to the development of ourselves). lack of flexibility is because of too much tension int he muscles. this is why people who bounce around forcing stretching when they try the splits are doing themselves tendon damage, they are fighting against muscle that want to contract out of fear. relax the muscles and you get more flexible (this is a long term achievement), do your neck rolls slowly so that you can willingly tell your muscles to relax, when you hit a spot that it hurts, slow right down and try to get the muscles to relax before rolling to the next area. relaxing your vocal chords to sing higher isn't the only thing relaxing relates to. relaxation = high skill in EVERY discipline.

I think this rumour about "tearing off muscle fibres" may come from the slight crunching sound you hear when you haven't done head rolls before or in a long time.
This crunching is actually the breaking down of calcium, deposited near the joint due to inaction.
It's totally normal, and if you do headrolls regularly, you'll never hear the sound again, and have a far more relaxed neck.