A licence is some sort of trust among gamblers to play on that particular casino but it doesn't imply that they cannot be scam as some of the other casinos have turned out to be scam even after owning a licence but still new legit casinos feel it obligatory to own a licence to increase the reputation and trust of gamblers before entering the market.
License is only beginning. Reputation requires more time to achieve and even good casino with good reputation can break its own reputation. We can not know when it happens but if it is an old casino with good reputation, we have something good and solid to put our belief on.
The safe approach is never put all money in one wallet, one cryptocurrency, one exchange, one casino. This approach is helpful to apply for casino too. I believe in Roobet.com casino because they are very good so far but as said, people should have their safe approaches and management for their capital.