Does the site respond slowly all the time, or just occasionally? Is it all sites, or just this one?

The network shots you posted (nice work on that, btw - makes it a lot easier) show some varying latency (which can be a sign of problems), but the generally low latency numbers really don't make me think of the network as a problem here.

You might try switching to the TCP packet type and use port 80 and see if that shows different results (since that's what your web browser is using). I'd suggest running for a longer period of time (an hour or two minimum) and looking for latency periods or packet loss. If you can correlate your slow performance with bad latency in PingPlotter, then this is what you'd want to send to RoadRunner.

I'd suggest collecting data for a while, then looking for problems, then sending the results (problems or not) to Roadrunner for help troubleshooting. It certainly sounds like a problem that's in the Roadrunner doamin to fix, at least - now you just have to convince them to help with the problem.