The key process parameters influencing built-up versus modified bitumen roofing materials include the type and concentration of modifiers (such as SBS or APP), the temperature during mixing and application, and the method of application (torch, cold adhesive, or self-adhesive). Additionally, the thickness of the layers, curing time, and environmental conditions during installation also play critical roles in determining the performance and durability of the roofing system. Proper control of these parameters ensures optimal adhesion and longevity.