Combine the peppercorns, sugar and lemon zest in a shallow bowl. Smash with the back of a wooden spoon until the peppercorns are crushed. Moisten the rims of 6 glasses with a little lemonade, then dip in the peppercorn mixture.
Combine the lemonade, gin and sparkling rose in a pitcher. Fill the prepared glasses with ice, then add the cocktail.