I hate their foreheads. It makes no sense--they are Vulcans, they are not similar, they are the same, because speciation doesn't happen in 2000 years. The makeup was a waste of money that could have been better used to make sure phasers didn't come out of the photon torpedo tube.
While from an evolutionary standpoint you're quite right...I can't help noticing the actors cast as Romulans tend to have a very different stature and build, in some cases, than those playing Vulcans. I personally like to reconcile it in my head by saying that the Romulans tampered with their own DNA to achieve a physique suited to a more temperate world like Romulus, as opposed to a desert like Vulcan. (Hell, maybe they even created the Remans as they experimented, either by accident or deliberately.)