In traditional stud poker games, cards are simply dealt to each player, either face up or face down according to the rules of the game being played, followed by betting. In roll your own games this is different in one of three possible ways. These are called:
In simultaneous choose-after in every round where an upcard is normally dealt, each player is instead dealt a downcard. All players then look at all of their downcards and choose one to turn face up, then all players turn their chosen card at once.
In in turn choose-after the game begins the same way with each player being dealt a downcard, but then the first player to act (determined by the rules of the particular game) turns over his choice of upcard, then the next player can use that information to decide which of his cards to turn up, and then all players follow in turn.
Choose-before is always played in turn. On upcard rounds, before a card is dealt to each player, that player must choose whether he wants to receive it up or down. If he wants to receive it up, he says so. If he wants to receive it down, he must first turn one of his already-dealt downcards face up, so that all players will still have the same number of up and down cards. When using this method cards are not dealt to players starting at the dealer's left as usual, but start with the high hand showing.
Roll your own should not be confused with rollouts, which, while similar, is fundamentally different.