Which material is typically used to cover the exposed surface of rolled roofing?

Rolled roofing typically uses a mineral granule surface for exposure, making slate the most appropriate choice among the given options. This method helps protect the roofing material from UV degradation and provides additional weather resistance. Mineral granules add weight and help to bolster the integrity of the rolled roofing material, making it more durable against environmental factors.

The other materials listed are less suitable for this application. Tar is commonly used as an adhesive or sealant in roofing but does not serve as an effective surface covering for rolled roofing. Plywood is a structural material and would not be used as a finished surface in this context. Vinyl is more relevant in siding applications and isn't used as a protective layer for roofing surfaces. The choice of slate, in this context, aligns with the industry standards for rolled roofing applications.