Combine rosemary, garlic, salt and pepper to form a paste.
Spread half of herb paste evenly over roast.
Add olive oil to remaining paste; place vegetables in large bowl; pour herb-oil over vegetables, stirring to coat.
Place roast, fat side up, on rack in open roasting pan; Arrange vegetables around roast (DON'T add water or cover).
Roast at 425°F for 35 to 40 minutes for rare to medium; Remove roast and peppers to warm platter, allow to stand 10 minutes.
Meanwhile increase oven temperature to 475°F and continue cooking potatoes and onions 10 minutes or until tender and lightly browned: add potatoes and onions to meat platter, carve roast against grain and serve with vegetables.