Well that's the question isn't it? Which 'period' of Romans do you want to go for? As far as Early Imperial, the classical Romans from the likes of Gladiator, and the style found on all those old films (even if the style of armour, etc... might have been out by five or six hundred years), with Loria Segmentum, etc... Then Steve Barber is the one to go for IMHO, it's what I went for anyway.
Late Imperial Roman, IIRC Pendraken are the guys that manufacture Clibinarium's figures, and quite frankly they are bloody gorgeous.
There are some Republican ranges available as well, but no late Republican as of yet. It is on my 'if I ever get the time' to-do list to have a go at sculpting some though, so watch this space. You might have to wait a while though, I first though of giving it a go about eight years ago...