Help with derma roller

[AshCro]

I have purchased a derma roller for a few cystic acne scars but as with many things I've read some horror stories so is it actually too risky to use them at home or do you have any advice? Wary of making my scars worse. I only have a few but they are really noticeable and I want rid I already use serums like vitamin c, acids etc but haven't really noticed a difference