Mashed Potatoes and Root Vegetables

2 tablespoons unsalted butter 4 ounces carrots (parsnips, turnips, or celery root, peeled, carrots or parsnips cut into 1/4-inch-thick half-moons, t) 3/4 lb[...]

2 lbs yukon gold potatoes or 2 lbs russet potatoes , peeled,cubed 1 cup sweet potato , peeled,diced (yellow variety) 1/2 cup rutabaga, peeled,diced 1/2 cup[...]