Preheat oven to 450°. Unroll piecrusts on a lightly floured surface. Sprinkle rosemary, pepper, and ½ cup cheese over 1 piecrust; top with remaining piecrust. Roll into a 13-inch circle. Press on bottom and up sides of a 9-inch springform pan; fold edges under. Press out as evenly as possible to avoid doughy areas of crust - this may cause some of the crust to come up above the lip of the pan - fold these under - or you can cut off and reform the edge of the curst. Chill in the fridge while you prepare the remainder of the dish.

Meanwhile, thinly slice Red potatoes - no need to peel, unless you prefer that look, peel the sweet potatoes, carrots and turnips.

Layer one-third each of red potatoes, sweet potatoes, carrots and turnips and salt in prepared crust. Sprinkle with ¼ cup cheese. Repeat layers twice, pressing layers down slightly to fit.

Microwave cream and garlic in a 1-cup microwave-safe measuring cup at HIGH 60 seconds; pour over potato layers in pan. Sprinkle with remaining ¾ cup cheese. Top with ¼ cup freshly grated Parmesan. Cover pan with heavy-duty aluminum foil. Place on a baking sheet.

Bake at 450° for 1 hour. Uncover and bake 25 minutes or until potatoes are done and crust is richly browned. Let stand 10 to 15 minutes. Carefully transfer to a serving plate and remove sides of pan. If desired, carefully slide gratin off bottom of pan using a long knife or narrow spatula. I was able to remove using two large and long spatulas