Talk to them out of game. Stress the importance of character cooperation for the good of the game. Ask them to come up with some kind of in character reason to cooperate.
Divine or infernal intervention? Having an evil character being a jerk and a paladin is a recipe for disaster for party cohesion unless they have a common cause (and even then it's no guarantee). According to the paladin's code, it can't be a long term association and only to overcome what he believes is a greater evil. He must leave if he feels the evil character is causing more harm than good.
Generally as GM, I don't allow evil characters in a mostly good group unless there is a VERY good reason for them to be there. Same thing with good characters in a mostly evil group, there must be a good story related reason or I won't allow it.
If I were traveling with a half-fiend rogue who try to steal from me at night I would not have to be a paladin to hang him, or at least kick him out of the group.
I think Crysknife has a good point. Think zombie apocalypse/walking dead. If one of the people inside the compound is causing trouble, you have to feed them to the zombies or everyone is going to die. On the other hand, one of the things around the table which annoys me as a gm is when players know another pc is holding out on them but have absolutely no reason in character to know this, but act as if they do. If the rogue is any good, the other characters (as opposed to players) really shouldn't know that the reason their stuff is missing is because Bob the NE rogue took it.
If I were traveling with a half-fiend rogue who try to steal from me at night I would not have to be a paladin to hang him, or at least kick him out of the group.
Have to agree there; pretty much any character of mine, regardless of alignment, would take issue from someone who tries to steal from them, or anyone else in the party, really.
On the other hand, one of the things around the table which annoys me as a gm is when players know another pc is holding out on them but have absolutely no reason in character to know this, but act as if they do. If the rogue is any good, the other characters (as opposed to players) really shouldn't know that the reason their stuff is missing is because Bob the NE rogue took it.
While metagaming is always something to be avoided, I would say that when stuff starts getting stolen by someone within the party, it's not exactly unreasonable to designate the rogue with a questionable moral compass as the prime suspect.
Stealing from the group is never ok.
That is something a group should talk about OOC. I for one absolutely hate it and I don't think it's ok just because the other guy is playing his Char.
There are things the you just don't do and stealing from the group or keeping part of the treasure secret is such a thing.
The rogue in one game I play in recently tried it and if he does that more often we'll have a more or less serious talk about it.
And I am fascinated that it is tolerated if the rogue steals from the party but not if the item crafter charges money for his work, even if it is only by not telling that he took the trait that saves 5% of the cost.
Well good storyline reasons the Paladin might decide to let the Rogue's kleptomania go...
They are all stranded on an island filled with all manner of undead and evil outsiders, with no obvious way of escape. They know an evil presence is behind the undead and manipulating events to try and release Rovagug upon the world.
See, that serves to get them working together short term, but only if both parties are willing to compromise. Due to his moral code, the paladin is compromising by even working with a character that probably has an evil aura. The evil rogue is expected to compromise by not working against the party. I think there would already be trust issues there just due to the celestial vs. devil relationship. It seems pathological to further press things by stealing from party members while surrounded by the undead and fighting against a dark force. If that is his character concept, I understand, but I would never let a player sit down to the table with a character that opposed to party cooperation.
I agree with the idea that you are going to need to have an OOC conversation with your rogue. I hate to stifle a players creativity, but when one character is an anathema to the rest of the group (as some other posters pointed out, it doesn't take a paladin to attribute the disappearances to the half-devil rogue), I would rather stifle one character than risk ticking off the rest of the party.
Still kids out there who wanna play evil? We stopped that years ago, because it's just causing trouble. Funless trouble that is.
Talk to the rogue player and let him change his alignment to non-evil.
Or make it really nasty:
Send a good cleric to help them with a holy word! :)
It doesn't even sound like your rogue player is playing a neutral evil character, sounds more chaotic evil, and stupid chaotic evil at that
I played a chaotic evil rogue once and we had a paladin in the group. Most of the time my character was more righteous than the paladin.
Finally one time after a tough battle and everyone was injured and only me and the paladin was left standing. I sneak attacked the pally and as he drop I whispered in his ear and said I wanted to do this from day one. My character mourned harder than anyone else of the passing of our paladin comrade. Hehe.
I hope you don't call yourself the pally-player's friend.
"But it fits my pc" doesn't make some things less no-go.