Q. Does sunlight reflected off a mirror raise the temperature of the sun-rays?

Answer:-

A standard planar mirror will not raise the energy contained in the rays that reflect off it. In reality there will be some loss of energy since the reflective surface isn't perfect. There is a few reductions in the light's intensity as it passes through the mirror's glass and reflects off the backing surface.

Parabolic mirrors on the other hand focus as well as concentrate the light rays on a single point in front of the mirror, aptly named the focus. Even though the energy is not amplified it will be effectively increased because of the additive effect that will result when the light energy is concentrated.