Hwy 50 to Montrose is a pretty standard route. Lots of scenery along the way up in the high country. Royal Gorge is okay, but touristy. Black Canyon of the Gunnison, just east of Montrose, is much more impressive. Used to be a national monument, now it's a national park, I believe. From Montrose go south on 550 to Ouray, over Red Mountain Pass to Silverton, and on to Durango. I always liked the drive to make a loop, perhaps from Mesa Verde to near Cortez, then up to Lizard Head Pass, to Telluride, and then back to Ridgway north of Ouray. You could return to Denver from Montrose by going north to Grand Junction, then east on I-70, also a pretty standard route.
If you had more time there are scenic route alternatives, but on your schedule I doubt you'll have a lot of time for it.