Step 1Gently muddle the roses and cucumber. Stir in the simple syrup. Cover and set aside for 24 hours, at room temperature, for the flavors to infuse, then strain. This makes a generous 8 ounces cucumber-rose syrup, more than is needed for the remainder of the recipe; the syrup will keep, covered and refrigerated, up to 2 weeks.
Step 1Muddle the lemon peels with the sugar, releasing the oils in the peel. Add the lemon juice, syrup, bitters and gin, along with enough ice to chill. Stir quickly to chill, then strain over a large block of ice. Garnish with rosebuds and top with soda.