Rock Garden - Arrrgghh!
I have only camped at Rock Garden once, and now vow never to return. The trains go through that canyon multiple times through the night, and they are loud. Camper Beware - unless you are totally wasted and/or can sleep through the end of the world, you will probably not get a peaceful night's sleep.
There is a BLM campground near Wolcott, probably not very full yet. get off I70 at Wolcott, and go about 1.5 miles west on HWY 6. Right by the river, and there are a couple large rocks there that folks boulder on (fun for the kids?). A little more than 30 minutes to Glenwood, but far less than 1 hour.