Well, if not T'Rul, then at least some
We've seen almost every alien race explored thru the presence of a main or continuing character. We've gotten substantial portrayals of Klingons, Ferengi, Vorta, Vulcans, Betazoids, Denobulans, even Andorians.
But as one of the major races in ST, Romulans have really been stiffed. And not even once, but again and again and again. They just never get a good shot, which sucks for me because Romulans were always very interesting to me.
Also Tellarites, but that's a whole other thing...