As mentioned above, riding from Vancouver to Alaska would take five days, but you could do it by going from Vancouver to Lake Louise/ Banff via the Coqihalla highway ($10 toll),(1 day) then head up the Icefield Parkway to Jasper, then west to Mount Robson and onto Prince George (2nd day)then up to Dawson Creek and the start of the Alaska Highway.All excellent paved roads. On the way down from Alaska you could turn south at Watson lake and go via Dease lake, Smithers,Prince George,100 mile House, then the Fraser Canyon to Vancouver.
Both of these routes are spectacular and well worth five extra days. I have travelled these routes several times and can supply more info.if you would like.
Good Luck, Cameron