In some of the casinos that run free spin will not allow you to withdraw bit you will use it to spin again until you finished you reward in the bets while some will all you to deposit first before you can withdraw the reward free the free spin.
But it is possible for one to make money (HAVE ENOUGH REWARDS) from free spins just that you have to be careful because if you wins big from free spin I don't think the company will release the amount for you. They would use some to hold your wins down until you make a huge amount of deposit before they can decide what to do.
^This must be found on the terms and it should be there, there must be a maximum wagered and the minimum amount to withdraw your winning on the free spin. There is nothing wrong if you will reach out to the gambling casino staff and ask them about this because each casino has different rules and guidelines when it comes to free spin. Trusted gambling casinos will usually allow users to withdraw their winnings on the free spin. But in OP's question, can we still win with free spin, that is depend on our luck, if you are very lucky enough and win a huge amount, that is good for you.
OP's question doesn't really have concrete answer as playing free spins depends on your luck.
But of course, the possibility of winning is always there, you just don't know when.
Several gambling sites found in this forum are offering free spins like freebitco, betfury, which I can say that they will give those winnings if you did win.
But for other casinos which are not found here, you may doubt if they will pay especially if you got handsome amount of winnings.
Also, remember, check the conditions that you need to meet before withdrawal, if in case you win from playing these free spins.