Not quite on the Denver-Vegas route (unless I-70 is still closed when you're driving), but Vedauwoo would be your best option around Denver. Tons of OWs of all difficulty, many of which are easy to set up top ropes on.
Indian Creek has a bunch of OWs too, but most of them are at least 5.10 since the walls tend to be more vertical. Though you can set up a TR and work the routes if you're able to aid up them first.