The "roar" test is also known as the viscous fan test.

Based upon temperature and RPMs, the viscous fan is suppose to engage at x-degrees and y-RPM, and disengage at z-RPM.

Viscous-Fan coupling airflow temp: 92-100C
Safety Cut-off Fan Speed: 4500, engine RPM 3250

Also, it's called a "roar" test because if it's hot outside and in the engine-bay, once you hit about 3500 RPM the viscous fan should be engaged and you'll hear the "roar" of the fan.

:-) neil
1988 360TE AMG
1993 500E