Roasting is when we blast the ore with air, like for zinc blende. Calcination is heating without air, for carbonates like limestone. Which ore uses which? It depends if the gangwa has to be driven off as gas or not, yaar.
But the book answer forgets the plant reality. Here in Jharkhand, for our low-grade haematite, we sometimes do a controlled roast even if books say it's not pure calcination. Why? Because the furnace man knows his fuel cost better than the professor. My bonus depends on saving that extra coal, so we adapt the 'perfect' process.
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