I can't imagine Rodney ever really calling John an idiot or a moron. I think Rodney finds John too irritatingly intelligent for that.

As John's frustrated grumble in Return 2 reminds us and Echoes very clearly demonstrates, he's often the one that 'figures something out' and then expects Rodney to expand on it, or sometimes simply to make it work. They're a great team, and I think whether he says it aloud or not, Rodney's quite aware of it.