Vennettai said:
Would he let stealling go moreso than a Paladin.
Theres alot of ways too look at this but first.... is that Player knowledge or did your Cleric see him steal?
If its player knowledge let it go. If it isnt you need to examine it closer.
Some things to consider (at least the way I would look at it if I was a LG Cleric of Heironeous...
How well do you know your companion? How long has he traveled with you? Do you think its his intent to profit "no matter the cost" and at the expense of others regardless if they are decent folk? does he have some redeeming morals?
If your character thinks he is good overall, then try to look at it as being his "way" through life. Its what he knows, its how he has survived, etc. You can roleplay trying to get him to better himself. At the same token, you should also consider that as a Rogue, he benefits the party, he has a place in the world just as the most good and just people have a place in the world.
If you think his motives totally unpure, you should confront him in a forceful but non-violent manner, and you might want to bring this to the attention of your whole party as well. I probably would roleplay a semi-cold attitude toward the rogue at this point until he would change his ways or at least halt the unecessary questionable activities in my presence. If he persisted in showing his disrespect by continuing his illicit activities I would move for him to be removed from the party or I would have my character remove himself from the party (being true to my interpretation of the character no matter the cost).
This has happened to my group before, the "either he goes or I go" scenario. Its a hell of a roleplaying opportunity, but it could lead to one of you having to leave the party and create a new character ... so if you go this route beware. We had fun with this when it happened to us and my players are great handling this kind of issue, even if they have to let go of a character for that character's convictions.
Hope that helps