Beat first 3 ingredients in a large mixing bowl at medium speed with an electric mixer 4 to 5 minutes or until smooth and creamy. Cover tightly; set aside.
Trim stem from 1 rose to 3 to 4 inches; wrap stem with florist tape.
Spoon 1/2 cup meringue mixture into a bowl; cover the remaining meringue mixture to prevent drying. Coat rose petals with mixture using a small, soft paintbrush, gently separating larger petals from closed bud to form an opening rose. Brush mixture around tight center bud (do not try to open). Sprinkle rose with sugar, shaking gently to remove excess; dry on a wire rack at least 8 hours (do not cover or chill). Repeat the procedure with remaining roses and leaves, 1 at a time, drying leaves at least 3 hours.
Note: Crystallized roses and leaves may be made up to 48 hours ahead. Be sure to select roses that are fresh and only partially open; keep roses in water and chilled until ready to crystallize.