We use TST services to make sure numbers are randomly generated, you can be assured it is provably fair. If a player has never deposited before we may require a deposit on free money, but most of the time we do not.
This doesn't sound great to me, in fact it's a little bit of a red flag. There are too many books in the past who screwed people over - you say "most of the time we do not" but that's not a rule, that gives you a lot of leeway. You could say "hey congrats you won, but now you have to deposit $1,000 to withdraw $100 bonus."