Sounds like, in those situations, you may not be getting yourself tucked up quickly enough? I had the *same* problem (and trust me, as the author of the original post in this thread, I'm not above saying I had tons of problems I didn't quite understand at the time!!
): once I got upside down, between opposing currents, the pressure of the water, the noise, I didn't know quite where to begin or what to do.
I think that's half the problem of practicing your roll when you're always "setting up": the fact is, when you get flipped on a river, you're not setting up, not waiting for it. To get your hands back around, and ultimately, to hit your roll, youve got to get back to that place that's familiar to you.
When you cranked over, no matter what position your boat is, no matter where you're being pulled, your first instinct needs to be getting yourself back to your front deck. Whether that means twisting, rolling your body with or against the water, whatever you need to do, get back to the front of the boat. With that motion, your arms will follow: the pressure on your paddle blade will be pretty great in some instances, but hang onto it. Sometimes it helps if you can get your paddle rotated in your hands so your blade is "on edge" with the current, i.e. so that the water slices along the length of the blade, rather than has the opportunity to pull against its face.
Now that I think about it, that's probably actually the best bit of advice I could give you here,.... if the water's deep enough, get your paddle into a position it works with you, rather than with current working against it. Here in the SE, we paddle things shallow enough we're getting grated over rocks, and that's half the challenge of getting your paddle back around-- it's getting dragged somewhere between you, your boat, the river bottom, and current!
But out in CO, as long as you've only got one element (water) to deal with, there's no sense in fighting it if you can make it work in your favor.
Holes can be the EASIEST places to roll on the river if you can just get yourself to that setup position.... once you're there, reach your hands WAY up over the bottom of the boat-- not just to the water's surface, but as far up as they'll go (keeping your elbows locked, and not overextending your shoulders or opening yourself up for any injuries). Pivot that right elbow/ blade outward, like you're opening up for your sweep, and feel for any "pillow" with your blade. If you can catch this, find purchase for your paddle and give it just a tiny bit of "angle" to grab onto, the hole's gonna do most of the work to roll you up itself. Provided you can get the river to do most of the levering work for you, all you have to think about at that point is your hipsnap....
As far as pourovers and eddylines go.... just be patient. When you get flipped, count to three. Don't think about anything, except that counting to three will give the current a chance to push you either over the eddyline, or swirl you to a place in the hydraulic with a little less resistance. Don't panic, don't think about swimming, don't think about "oh shit!"
Just count to three, keep it setup, stay calm, and find your opportunity to roll.... half of consistent rolling's in learning to be patient with it, especially at first.