Calcination is the process of converting carbonate and hydroxide ores to oxides by heating them to temperatures below their melting points while avoiding or limiting the presence of air.
This process, for example, converts carbonates of Ca, Mg, and Zn into their respective oxides.

ZnCO₃ ⇒ ZnO + CO₂

Fe₂O₃.3H₂O ⇒ Fe₂O₃ + 3H₂O[Heat]

Roasting is the process of converting sulphide ores into their metallic oxides by heating them over their melting temperatures in the presence of air.
This method, for example, converts sulphide ores of Pb and Zn into their corresponding oxides.

2Zns + 3O₂ ⇒ 2ZnO + 2SO₂

2Pbs + 3O₂ ⇒ 2PbO + 2SO₂