Preheat the oven to 350℉. Spray an 8x8-inch pan with nonstick spray.
On a lightly floured cutting board, unroll the crescent dough, and separate into 4 rectangles. Pinch the perforations to seal into four rectangles. Spread each rectangle with mustard, and top with ham and cheese. Starting from the short side, roll up each rectangle, pinch the edges to seal, and slice into 5 to 6 roll-ups. Place them cut-side-up in the baking pan.
In a small bowl, whisk the melted butter, parsley and garlic powder. Brush this mixture over the pinwheels and sprinkle with the poppy seeds. Bake until golden, 12 to 15 minutes.