Step 1In a small saucepan over medium-high heat, bring sugar, rosemary, salt, and 1/2 c. water to a simmer. Reduce heat to medium-low to maintain a gentle simmer and cook, stirring often to dissolve sugar, about 2 minutes. Let cool slightly.
Step 2Transfer syrup and rosemary to an airtight container. Refrigerate until ready to use.
Step 3Make Ahead: Syrup can be made 3 days ahead. Keep refrigerated.
SPRITZ
Step 1In a shallow bowl or plate, mix sugar and paprika.
Step 2Gently rub edge of a tall glass with grapefruit wedge, leaving a small amount of juice on rim; reserve wedge for serving. Roll glass in sugar mixture to coat rim.
Step 3Fill glass with ice. Add sparkling water, grapefruit juice, and 3/4 oz. rosemary syrup. Using a cocktail spoon, stir to combine. Push rosemary sprig through center of reserved grapefruit wedge and garnish glass.