<p>In present times, industrial conversion of zinc sulfides to oxides (calcine) is customarily done in fluidized bed roasters owing to efficiency and productivity. Degree of such roasting is quantified in terms of the sulfide-sulfur index describing extent of sulfides being unreacted and high index affects the downstream leaching efficiencies. Generally, roasting is multi-process parameter (viz., feed rate, airflow, and moisture etc.) dependent and essentially particle residence time of the feed concentrate inside roaster. Present study deals with assessment of roasting process from lab-scale analyses of feed and calcines collected from different roaster locations. Toward this, characterization, minerology, chemical assay and plant data monitoring have been done. Results of such indicated the calcine ranges where extent of roasting is minimal accompanying role of concentrate characteristics (i.e., composition and size) on roasting efficiency. Finally, possibilities of precious metal recoveries from calcines have also been outlined that effectively lacked in past investigations.</p>