I own both the I roast I and II and both are a few years old. Through, a little research, I've discovered that apparently there were differences in power out put, between the four different series of models that Hearthware has made of the I-roast machine. I just happen to have two that have the lower power output and hence cooler roasting temperatures. I currently roast a french roast bean to a bit beyond full city.
Any air roasting machine is of course working with the current air temperature and as I roast outside, the perfect solution has been to place the roaster into a round 10 gallon, rubbermaid cooler. I then cover the top with a thin coarse weave blanket. The coarse weave works to allow some air to escape yet traps in quite a bit of heat. This is not a set it and forget it operation. One must attend the blanket and remove and then cover back for 15 seconds then remove again and so forth. The point of this being to get the beans to ramp up to temperature quickly, then allow the roasting to proceed from there, uncovered. The only risks are, in leaving the blanket on for too long, are, building up too much heat and shutting down the machine and two, roasting the beans at too fast a rate, which you will taste. Hope this is helpful to anyone out there dealing with this delema, Cheers, Russell