((1) Does "refined" sugar mean granulated sugar? Can I use caster sugar? (2) What temp is the "preheated oven" to roast the cashews?

I roast a lot of nuts. I preheat the over to 250 degrees F, spread the nuts on parchment paper, in a sheet pan and roast for 12-14 minutes. Check them, you can always roast them more.
No idea on the sugar