Stir together sour cherry juice, sugar, and salt in a medium bowl until sugar dissolves. Stir in rose (you should have about 3 cups).
Prepare an ice-water bath. Sprinkle gelatin over 3/4 cup cool juice mixture in a small saucepan, and let stand until softened, about 5 minutes. Bring to a simmer over medium-high heat until gelatin dissolves. Strain gelatin mixture into remaining juice mixture in a bowl set in ice-water bath. Let stand, stirring occasionally, until mixture begins to gel, about 15 minutes.
Stir in sweet cherries, then divide among 4 bowls. Refrigerate until just set, about 1 hour or up to overnight. Top with sweet cherries, and serve.
Consider the container as you go; by using delicate, shallow white bowls instead of gelatin molds, we highlighted the jelly's bold hue with sophisticated results.