Rosewill PSU's are low quality and possibly the sources of your crashes, I'd replace that with a good quality unit such as Corsair-SeaSonic or XFX.
The GPU maybe overheating, but before we check that, please boot into the bios and check the voltage readings. You'll find them under "system health status" where the CPU temp readings are located.
The GPU maybe overheating, but before we check that, please boot into the bios and check the voltage readings. You'll find them under "system health status" where the CPU temp readings are located.