I don't know what "higher roast" is, but if you're talking about dark roast, then 100°C is pure madness!
I brew my dark roast at 85°C using a ceramic Hario V60. I do preheat it though.
With that said, I don't recommend a specific temperature, but you should perhaps not be afraid to experiment with lower temperature.
And don't forget to check out Lance Hedrick on YouTube. He have a tons of tips and recommendations for the best brew that you can make with your equipment and your water.
No. And the dev(s) have said that they refuse to implement such feature. :(