The present investigation involved the production of roof tile samples through the replacement of kaolin clay with varying proportions of Ferrosilicon slag (FS) (0%, 10%, 15%, 20%, and 25% by weight) at different firing temperatures (900 °C, 1000 °C, and 1100 °C). The present study investigated the impact of incorporating FS slag waste on durability, mechanical strength, thermal shock resistance, and thermal properties. Furthermore, an examination of the microstructure of the fired roof tiles was conducted through SEM analysis. The properties of the roof tiles exhibited enhancement as the percentage of FS slag increased, reaching a maximum of 15%, and the firing temperature increased up to 1000 °C. This can be attributed to the formation of significant amounts of corundum phase. Increased temperature and a higher percentage of FS slag are associated with the generation of a significant quantity of cristobalite phase, resulting in a reduction in the mechanical properties of roof tiles. The roof tile samples fabricated with up to 15% FS slag at 1000 °C exhibited low water absorption and porosity. Increases in temperature and FS slag, on the other hand, resulted in an increase in water absorption and porosity. There were no observable impacts on water absorption and apparent porosity at 900 °C. The firing temperature of 1000 °C and a slag percentage of 15% resulted in a minimum water absorption of 9.8%. This value meets the standard requirements for moderate weather resistance. Notwithstanding the increase in density of roof tiles containing elevated proportions of FS slag, they continue to fall within the limits of lightweight roof tiles as stipulated by determined standards. The experimental results indicate that the incorporation of 15% FS slag and firing at a temperature of 1000 °C resulted in a significant increase of 34.9% in the transverse breaking strength (TBS) of the clay roof tiles when compared to the conventional sample. This suggests that the structural properties of the clay roof tiles were improved through the addition of FS slag.