2003 Jeep Cherokee Roaring noise at stopllight

After driving at highway speeds, the temperature guage shows an increase in temperature past the middle point on the guage. Also, if you have to stop in traffice or at a stoplight on the highway, there is a roaring noise coming from under the hood. The engine rpm's are at 600, but the noise is just a roaring sensation. When you shut the engine off, it is a hard shut down. You can restart, and the roaring noise is gone and the Jeep is fine until you reach 65 mph again. Is it a radiator fan problem?