The superlative form of the word 'rosy', meaning the most pink or red.
The word 'rosiest' makes people think of happiness, health, and good things.
Examples:
The flower is the rosiest of all.
She has the rosiest cheeks.
The sky was the rosiest I've ever seen.
His cheeks turned the rosiest color when he saw her.
The rosiest sunset painted the whole sky pink.
The rosiest apple was the best one to eat.