Place rib roast, fat side up, in heavy roasting pan. Mix 4 teaspoons crushed rosemary, salt, and pepper in small bowl. Stir in 1/2 cup oil. Rub mixture all over roast.
DO AHEAD Can be made 1 day ahead. Cover and chill. Let stand at room temperature 45 minutes before roasting.
Combine 2 cups boiling water and porcini; let soak until mushrooms soften, about 20 minutes. Strain soaking liquid through fine strainer set over measuring cup; reserve porcini. If needed, add enough water to soaking liquid to measure 1 cup. Coarsely chop porcini.
Melt 2 tablespoons butter with remaining 2 tablespoons oil in large skillet over medium-high heat. Add fresh mushrooms; sauté until browned, about 6 minutes. Add porcini and garlic; stir 1 minute. Remove from heat.
Combine flour, remaining 2 tablespoons butter, and remaining 2 1/2 teaspoons crushed rosemary in small bowl; mash with fork to smooth paste.
DO AHEAD Porcini soaking liquid, mushroom mixture, and flour-butter mixture can be made 1 day ahead. Cover separately; chill.
Place rack in bottom third of oven and preheat to 350°F Cook roast until instant-read thermometer inserted straight down into top center of roast registers 125°F to 130°F for medium-rare, about 2 hours 30 minutes.
Transfer roast to platter; cover loosely with foil and let rest 35 to 40 minutes.
Skim any fat from top of pan juices (there will be a small amount of pan drippings); reserve juices in pan.
Set roasting pan atop 2 burners over medium-high heat. Add reserved 1 cup porcini soaking liquid, broth, and wine; bring to boil, scraping up any browned bits.
Add mushroom mixture, then butter-flour mixture; whisk constantly over medium-high heat until sauce thickens, about 2 minutes. Season sauce to taste with salt and pepper.
Garnish roast on platter with fresh rosemary sprigs. Slice roast and serve, passing mushroom sauce separately.

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Nutrition Facts

Per Serving Per 100 g

Amount Per 1 Serving
Calories	1295.94 Kcal (5426 kJ)
Calories from fat	993.29 Kcal
		% Daily Value*
Total Fat	110.37g	170%
Cholesterol	268.67mg	90%
Sodium	559.49mg	23%
Potassium	859.16mg	18%
Total Carbs	15.45g	5%
Sugars	0.63g	3%
Dietary Fiber	1.69g	7%
Protein	59.59g	119%
Vitamin C	1.2mg	2%
Iron	7.3mg	41%
Calcium	51mg	5%

Amount Per 100 g
Calories	279.72 Kcal (1171 kJ)
Calories from fat	214.39 Kcal
		% Daily Value*
Total Fat	23.82g	170%
Cholesterol	57.99mg	90%
Sodium	120.76mg	23%
Potassium	185.44mg	18%
Total Carbs	3.34g	5%
Sugars	0.14g	3%
Dietary Fiber	0.37g	7%
Protein	12.86g	119%
Vitamin C	0.3mg	2%
Iron	1.6mg	41%
Calcium	11mg	5%

* Percent Daily Values are based on a 2000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
Find out how many calories should you eat.

Tastes

salty
savory
bitter
sweet

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