During roasting is sulphur dioxide always formed
2)during calcenation is carbon dioxide always formed?

In roasting, air in large amounts, sometimes enriched with oxygen, is brought into contact with the sulfide mineral concentrate. This is done at elevated temperatures when oxygen combines with sulfur to form sulfur dioxide and with the metal to form oxides, sulfates and so on. ... Roasting is an exothermic reaction.

calcination as "heating to high temperatures in air or oxygen

Explanation:

answersilicon (si); oxygen (o);