I have written before about fake rollers and their risks. Buying a quality derma roller is important for several reasons. For example, its needles must be made of surgical grade steel, not just 'stainless steel'. And the finer they are the better. Also, the roller should be properly pre-sterilized, otherwise it puts you at risk of infection.
The best roller is still, in my opinion, Dr. Roller (see my review) made in South Korea. Other reasonable brands are MNS and ZGTS (although I must say I only tried the latter).
For a long time I avoided linking to an online store that sells rollers, but recently decided to link to my favorite shop in the condition they give some kind of discount to readers of this blog.
This shop is Dr. Roller SHOP, and you will get a $5 discount on each order by using the coupon code 'newroller'!
You do not need to worry about their products, I can tell you they are genuine. In addition, their prices are the cheapest that I've found, and they ship worldwide (from Europe).