If anyone starts to cast a spell or attack initiative is rolled. Combat rounds are over in seconds in game time, the fact that it may take a few minutes is just there because we can't process multiple simultaneous actions in a PNP game.
I assume that starting to cast a spell is always the same, by the time it gets to the initiative of the caster they can change their mind.
There are exceptions of course where some or all of the participants will be surprised the first round. The rogue may try to pull the dagger with a sleight of hand, the sorcerer may have silent stilled spells and so on.
I assume that starting to cast a spell is always the same, by the time it gets to the initiative of the caster they can change their mind.
There are exceptions of course where some or all of the participants will be surprised the first round. The rogue may try to pull the dagger with a sleight of hand, the sorcerer may have silent stilled spells and so on.