gotta be many options.
what are your time constraints?
wanna do some dirt/gravel or stick to pavement?
wanna see some national parks?
plan to do any hiking?
do you need a relatively direct route, or can
you meander into northern new mexico for example?

if you wind up heading west from denver area,
I70 at glenwood is a groovy ride.
pretty sure there's a bike path thu there as well.