Keystone to Glenwood Springs is mostly trail, and all of that paved. Where there is no trail, you would ride on the old US 6 highway that serves as the frontage road for I-70 and has very little traffic. It's only 105 miles and not the midwest, but there are more than enough nice views of nature. There is some elevation gain on Vail pass, but westbound you're going the easy way.
https://www.google.com/search?q=keys...ings+bike+path
I aslo find it very strange why you would pick the Carpenters Training Center near Robinson, as you starting location. Which just happens to be a couple of miles from my home.;
I ride by there very often on weekend rides.