Final answer:
Rosacea results from the dilation of small facial blood vessels, which is caused by vasodilation.
Step-by-step explanation:
Rosacea is a skin condition characterized by the dilation of small facial blood vessels. The cause of this dilation is vasodilation, which is the widening of blood vessels. Vasodilation allows more blood from the warm body core to flow close to the surface of the skin, resulting in the characteristic redness associated with rosacea.