I'll jump in here with a few of my favorites I have biked. I like to get around.
Colorado. Anything is good but 14 into the Rockies from Ft. Collins is swell. And I adored the Leadville area.Downtown Leadville has a great Irish Pub.
Mt. Evans you can ride yer bike nearly to the summit of a Fourteener.
Around Rapid City dont miss Vanocker Canyon, Nemo Road, and The Needles Hy. But not during bike week. Too crowded.
Wyoming Hy 14A
And The Chief Joe and The Beartooth Hy into Montana.
Montana has Going To The Sun Highway in Glacier National Park.
And Looking Glass Highway south of St. Mary.
Watch out for bears, beef cows, and horses on Looking Glass.
Yer this close to Idaho might as well find 77 miles of bliss on Hy 12.
But the best I have found is the New Denver area of British Columbia. Top shelf roads and few cops. And a few free ferry rides.
A link to some great,great B.C. roads. Top shelf riding in the Kootenays.
Have fun. There's a lot to see out west.