A lot of good advice here - I am currently running a game with another DM and 11 players (yep those number are correct) As you can guess - there are several different styles involved and the balance has to come from us (my co-dm and I) in many ways.
My first suggestion would be to let him play the cleric and focus on a war style domain/pantheon. Then during game play make sure that you help him develop that pantheon to more than just a means to an end. (ie - i want power so I play a cleric) What about holy days, sacrifices, tithing, enemies of the order, political ties or severed political ties, family emninty about the order, etc. Many times we can get so used to playing the game that during the basic creation of characters phase we as DMs forget that we too have to be in the trenches as it were in order to seize upon things the players have (or in this case haven't) written about their character's past.
You may find that "Bob" hasn't ever had a vested interest in his character's feelings (ie roleplaying) simply because he is strictly in "video game mode" make character, kill monsters, collect rewards, repeat ad inifinitum. If you pull him into a character driven plot based on his charcter (talk to the others that have complained and get them to support you in this endeavor) you may find he has had the tools, but not the motivation to be an excellent roleplayer (something we have had to do on several occasions in my current campaign)
I am not excusing his behavior, nor do I condone it, but there may be things the whole group can do to subtely push him in the right direction versus clubbing him over the head with it. You might find that your DM skills, your player's rolwplaying skills and the overall game will be much better for it.
But that's just my two coppers!