I'd say C-Roth, C-Barcelona and IMA are as fast as you're going to get.
I found the change in Roth waves has actually made it a bit more difficult as you're placed with similar abilities and find yourself fighting through the funnel towards the end. You might only lose a few mins but it'll take more energy out of you for the rest of the race.
At the end of the day it comes down to a fast bike course and a flat run (weather dependent). I have done 4:46 at Roth on two occasions and I class myself as a runner. If you can nail a 5:30 bike (good runner) or 5:00-5:15 weak runner then you're done.