Preheat oven to 400 degrees. Set a medium pot of water to boil.
In a large bowl, toss potatoes with olive oil, salt and pepper. Spread potatoes out on a baking sheet and roast for 35 to 40 minutes or until the potatoes are tender when pierced with a knife.
Once water is boiling, blanch broccoli rabe for 2 minutes, drain well and set aside.
Melt 1 Tbsp. butter in medium skillet over medium flame. Add sage leaves and cook 3 to 5 minutes, or until darkened, crisp and slightly curled. Remove from pan and set aside. Add garlic and 1 Tbsp. butter to the pan; sauté for one minute and add broccoli rabe leaves. Cook, stirring occasionally and lowering heat as necessary to prevent scorching, until rabe is tender, about 5 minutes. Transfer to a dish and serve with roasted potatoes and crispy sage.