Roll I guess - and thats probably why I never could get into PnP groups for very long. I noticed the DMs would call rolls when they didn't want X, ignore rolls on Y, etc. It became wonky, because basically the DM was just telling us a story and we were interacting a bit. Thats a story, not a "game" to me - and they were pretty thin, extemporaneous type things.
Maybe I just had wonk DMs, or was bad at suspending disbelief. But when a table of Texans get around a table and they all start trying to sound like dwarves and elves it sounds ridiculous, no way in hell to stay immersed. So for me, I'd have preferred someone who bought a module and guided us through it as an arbiter rather than acting the role of Q from Star Trek.