It is very not appropriate to use the term 'safe' in gambling or even in online gambling using bitcoins. It should how much risk will you encounter in bitcoin gambling? We know it is online and I can think of many instances of cheating like that the operators can modify the results. But so far, successful crypto gambling sites are proving that they are fair but casual gamblers  need to be careful because they always like to try new gambling sites that leads them to a scam.