The Cool Roof Rating Council (CRRC) has a Product Rating Program, which lists the applicable test methods for testing these radiative properties. Their web address is:
For Solar Reflectance you can use either ASTM E903 or ASTM E1918. E903 is good for any roof type unless it is variegated. E1918 is used for variegated roofing products.
For testing Infrared Emittance you can use either ASTM C1371 or ASTM E408.
Actually I'm looking for a test method that can be used for ANY material, not just roofing. Is there anything about ASTM E903, ASTM E1918, ASTM C1371, and ASTM E408 that precludes their use on materials other than roofing? My application is the design of outdoor electronic equipment.
Go to the ASTM website and review the abstract info available for each standard. I am attaching the link to ASTM E 903, which is not specific to roofing material: