An ore-roasting kiln having a curved or sloping roof from which the heat is deflected onto the material being treated. The fuel and the charge occupy separate areas in the kiln so that there is no direct contact between them, thus avoiding contamination of the ore with fuel particulates. The heat rising from the ignited fuel impinges on the curved roof and is reflected downward onto the ore. After passing over the ore, the heat escapes through suitably located vents.