Combine first 4 ingredients in a medium saucepan, stirring well. (Frozen berries do not have to thaw first.) Cook over medium-high heat, stirring constantly, until thickened (about 10 minutes). Set aside, and cool.
Roll dough into an 18" x 9" rectangle; brush with melted butter. Spread cranberry mixture over dough to within 1/2" of edges. Sprinkle with walnuts, if desired. Roll up dough, starting at long side, pressing gently to contain filling; pinch ends to seal. Cut roll into 16 equal slices (about 1 1/8" thick).
On lower third of a large greased baking sheet, arrange 5 slices, cut sides up, in a row with edges touching. Form tree with additional rows of rolls, ending with 1 roll on top of tree and 1 roll on bottom for trunk.
Cover and let rise in a warm place (85°), free from drafts, 30 to 45 minutes or until doubled in bulk. Bake at 350° for 20 minutes or until lightly browned. Carefully remove from baking sheet, and cool on a wire rack.
Place frosting in a 2-cup glass measuring cup. Microwave, uncovered, at HIGH for 20 to 25 seconds or until drizzling consistency; drizzle over bread.