You know I have often thought ithat the TOS era Klingons and Romulans roles were flipped in the TNG era, myself. In TOS the Romulans were the honorable adversaries while the Klingons were duplicitous. But upon further thought, I don't think that is exactly what happened.
When you think of it, TOS Klingons being treacherous and like TNG-Romulans was only true in Errand of Mercy and Trouble with Tribbles. In Day of the Dove, they seemed more like the TNG era Klingons. In TMP we really didn't get a sense of the Klingons being honorable, but they definitely were militaristic. In TSFS, Kruge, though he was a renegade (much like Kirk was as well), Kruge was doing what he thought was honorable for the Klingon Empire and even seemed to treat Kirk with respect (momentarily) when he first found out he had Kirk's son killed. In TFF and TUC, you had both treacherous Klingons, but also honorable ones, too.
The Romulans were paranoid about the federation in both the TOS and TNG eras. We also have seen both treacherous Romulans, and honorable ones. I don't see much difference in the way they were portrayed in the two eras. Also, one must remember most of the time when someone is referring to Romulans as sneaks, betrayers, and dishonorable, it is usually Worf or some other klingon, and their view is not exactly unbiased (Worf in particular since his parents were killed by Romulans, and he almost had to take the wrap for a Duras\Romulan plot). But when you get down to it, there are as many examples of Klingons acting dishonorably in both TOS and TNG, as there are Romulans. Also, Sela, while one of the most treacherous Romulans, was also half human, and had an ax to grind against the federation and Picard, so she was more willing to get the better of them by any means necessary.
So, I think Ron Moore only expanded upon the Klingons and Romulans as they had been previously portrayed and did not intend a role reversal.