Betking.io turned into a scam website. If I remember correctly, it had one or two attempts to come back but it failed. Rollin.io closed their website very early and safedice.com had some problems in the past. Their owners disappeared out of nowhere and there were rumours that the owner got arrested and could no longer manage the website, so it was alive till the domain name expiration, then someone bought the domain and for some reason, decided to upload the HTML of old webpage. The current safedice.com is not old safedice.com, it's someone's phishing attempt.
At the moment, Primedice is the only one that remains alive. You can gamble on PD safely if you wish, they are still active.