For the simple syrup: Combine the sugar and water in a small saucepan and bring to a boil, stirring to dissolve the sugar. Add the rosemary and remove the pan from the heat. Let steep for 30 minutes before straining.
In a cocktail shaker filled with ice, combine the lemon juice, Scotch, bitters and 1 ounce of the simple syrup. Shake for 10 seconds; then strain into two rocks glasses over ice. Serve garnished with lemon wedges.