You do realise that the one way to ensure that Roger doesn't use a particular theme is to suggest it to him, don't you? Even if, by pure coincidence, he was in the middle of doing just that very thing, he'd be forced to scrap the idea because someone else had suggested it. It's a mixture of professional pride, more professional pride, and downright control-freakery, that I understand only too well.
You'll have to be a bit more subtle, Mincey.