I think when you have invested an amount to a casinos bankroll, you should look out for it all the time, when you've reached a profit with your desired amount (probably what you want or achievable results) you should withdraw it. I'm not sure if it will work because I haven't tried investing in one. Probably in the future.
based on my personal experience investing in gambling site always make your heart beat , you know why? it is because there always ann unexpected winning from players that causing the investors money get dropped to negative.
it is like how the real gambling work , you will hard to divest your money , you will always want more.