You can purchase them on https://zapple.com/exchange
There's also on https://hitbtc.com/CSNO-to-BTC but as usual, many bad reviews where made on hibtc.
Bankroll investment on the same casino which did have an ICO before is a bad move, unless it is agreed by current token holders as well as the purpose is clear which might be used to increase max win or to hold big prize contest in which their current asset can't support it, otherwise seem much more like a scam. If bitdice decide to have bankroll investment without major support then it will fall into the blood bath similiar to betking.
Since there was a good move which lock CSNO token at 400 satoshi (haters can't dump), they might just release a next round ICO if there is demand for the token (users can't buy in exchanges).