Hiking in from Road's End, via Roaring River, Colby Lake, and Colby Pass is about 31 miles one way and 14200 ft cumulative elevation gain. From Colby Pass to the Centennial Peak it looks simple to just follow the two connecting ridges, but it is easier to first drop down 100 ft or so on the south side of Colby Pass, traverse towards Centennial Peak staying roughly at that elevation avoiding the exposure of the first ridge, and then climbing straight up to Centennial Peak.
Peak view: https://www.google.com/maps/views/view/110594159553350261589/gphoto/6025224155164118402