BiggusGeekus said:
Now as a roleplay encounter things get weird. Let's say our troll has skill ranks in Perform (musical theater) and Knowledge (broadway hits). The troll will not hand over an item the PCs need for a quest until they help the troll put on a performance of The Music Man for the troll's true love. How exactly do we rate this encounter? What level is it appropriate for? As Hussar noted, what if the party is made up of four bards? What if the party has no bards at all? Do we let the PCs make a Perform skill check and call it a day? If they fail the skill check, how are they supposed to get the quest item without killing the troll? Because if they end up killing the troll, the DM may as well have made it a combat encounter.
AFAIK non-combat encounters don't have a system for assigning experience points - CR is only for combat encounters.
I have always assigned XP for non-combat encounters equal to that of an encounter (and in 3E terms - an encounter of CR equal to party level) assuming that:
1. the amount of time to resolve the non-combat encounter is roughly equal to a combat encounter
2. there is something significant to gain or lose in the encounter
3. the PCs did a reasonable job of it, and were mostly successful
To the degree that any of 1-3 is less/more, I adjust accordingly.
In terms of a skill-check type roll, I would guestimate that the DC would be 10 + character level x 1.5. So if the PCs have to beat a DC 20, that's about a Level 6 encounter. If the party has no bards, it will be tougher, but then again combat will be tough for a party of all bards, so it all balances out.
Whether or not you allow a single check to resolve or multiple I really think depends on how you want to design it. Obviously if you want to spend more time on the details of the encounter, set it up as a flow-chart so that a number of skill-checks navigate you through the situation.
'PCs killing the troll' is something that anyone running a DnD game should be ready for (the PCs do carry weapons after all, and most enjoy using them). In the case where the encounter devolves from broadway production to DnD slugfest, then I would give combat experience, and readjust whatever non-combat experience based on a lack of factor #2 above.