Right now it's exactly the same as D:OS2. You can't participate in a conversation, you can't change out party members mid conversation so they can do the rolls, etc. You can visibly vote on which dialogue option to select if you're watching, but that's it. You will also occasionally get the ! above your coop partners head and get the decision between two dialogue options, just like D:OS2. I'm really hoping this changes. The first Divinity had such a better and more entertaining system for this sort of thing, and it could be even better in this one. Pathfinder lets you make the rolls based on who is in your party, for example. Being able to delegate that stuff would be fantastic. As it is now, you don't even see the rolls in a conversation unless you're the one making the roll/controlling the convo.
