Place watermelon chunks in the blender and blend until smooth. Pour the watermelon juice through a fine mesh sieve, into a bowl and make sure you discard any seeds and pieces.
Mix in the rosé, lime juice, sugar and salt. Mix everything together well, making sure that all the sugar has completely dissolved.
Pour the mixture into a flat pyrex dish, cover with plastic wrap and place into the freezer. Freeze the mixture until the edges begin to set, about 2 hours (times may vary depending of the type of pan used.)
Once the edges set, use a fork to scrape up any frozen bits. Continue freezing, breaking up, and scraping the mixture every hour until it resembles fluffy shaved ice. Serve granita in cups with a spoon.
