There’s a nifty little site called AnyDice that lets you play with some dice probabilities and makes pretty charts and graphs for you. You can do some basic stuff pretty easily, and with a little bit of programming, you can model some pretty sophisticated probability curves.
I have to say, I mess this up all the freaking time when I GM. If something doesn’t matter, why are we spending our time at the table rolling for it? I think I could speed up play by improving here, but I want Lost Worlds to try and be pretty clear about when you should roll, and when you shouldn’t.
The idea of rolling to attack has been central to D&D since the very beginning. However, the game has been inconsistent about non-melee attacks in this regard. The concept of “saving throws” as defenses actively rolled by the players made the defensive side feel more active. It let players feel like they had the control in their hands when it came to surviving major non-melee attacks like a dragon’s breath weapon or ingested poison.
The question of who rolls in a given situation is a pretty important one. If you have to roll, you’re necessarily engaging with the mechanics of the game. You presumably care about the results of the roll, and so making the player the active roller in a defensive scenario seems like kind of a bright idea.
It’s hard to get too far down the road of designing an RPG without discussing the action resolution mechanic. Having played almost exclusively D20 games, it’s hard to imagine using something else, but I’ve been spending a lot of time thinking about this lately.