Preheat oven to 350°. In a large bowl, whisk flour, baking powder and salt. Cut in butter until mixture resembles coarse crumbs. Add milk; stir just until moistened (dough will be soft and sticky).
Turn dough onto a floured surface. Roll into an 18x12-in. rectangle. Sprinkle brown sugar and cinnamon to within 1 in. of edges; top with apples. Roll up jelly-roll style, starting with a long side; pinch seam to seal. Using a serrated knife, cut into 12 slices. Place in a greased 13x9-in. baking pan, cut side down.
In a small saucepan, combine sauce ingredients; bring to a boil, whisking to blend. Cook and stir 3-4 minutes or until thickened. Pour over top.
Bake, uncovered, until golden brown and bubbly, 45-55 minutes. Let stand 10 minutes before serving.