I've had exactly the same problem, and finally just resorted to driving up to Glenwood Springs and running Shoshone & Grizzly -> Two Rivers Park. The Grizzly -> Two Rivers is a few miles and generally deep enough and moving the whole way, so you can practice moving water rolls to your heart's content... but yes, requires shuttling. I'm lucky, we do it with 3x boaters, and just take turns shuttling using one car. Drive up early, make a day of it, get a few runs in.
I've also done the spot in the Platte about 3/4 mile below Confluence, but the water is probably too low by now and it's always kind of cesspool-like.
There's a spot at the bottom of those 5 or so features under the overpass that's just a tiny wave, flow and eddy. So you can practice peeling out of the eddy, into the flow, roll, rinse, repeat. And you can run the features over and over again with minimal walking back up to the top. Then make sure you do a nice good scrubbing of your gear and get a vitamin and antibiotic panel in you pronto. The Platte is extraordinarily disgusting.
And /agree, Golden PP is too low and once it's roasty in June-August, you dodge too many swimmers/tubers/idiots/kids.
I know that's not super helpful, but I'd be very interested in find out from the pros around here what their thoughts/tips/tricks are for places that aren't as far as Glenwood Springs (from Denver) and moving/deep enough water to practice rolls.