Children built snowmen with rosy cheeks.

Meaning: This means the children were making snowmen that had pink and healthy-looking cheeks.

Choice of Words: Children are young people, and built means to construct or create something. Snowmen are figures made of snow, usually shaped like people, and rosy means pink and healthy-looking. Cheeks are the sides of the face below the eyes. So, the sentence is saying that the children were making snowmen that had pink and healthy-looking cheeks.