I don't know that they work better for storage--it depends on if they are sized right for your junk and if you're storing stuff that is likely to stay put on a rollout. Like large appliances might do better on a rollout than in a drawer.

But drawers are a heckuvalot easier to use!

What's a framed roll-out?
Isn't that a drawer?

Why would you want to open a door, then pull out a rollout, when you you could just open a drawer? I can see adding a rollout to an existing lower cabinet, but can't see building a new one that way.

The highest capacity, but less convenient, is just to have a shelf.

Most rollouts that I have seen don't have high enough sides, so things tend to escape over the sides and back. This is maybe more problematic with framed construction, since stuff hanging over the sides can catch on the frame as you pull out the rollout.

how many cabs-if only a few I might order carcasses and fit them up with my preferred options ordered from online "all cabinet parts" or rockler or hafele or container store etc. you can get roll outs with higher sides or chrome roll outs or whatever. Do you have some 9-15 in width sizes-ordering carcass with a front would allow the roll out pantry with adjustable or fixed shelves or chrome or wood-you choose and DIY and save from what the cabinet company would charge. this is a bit of homework-looking at your sizes and thinking what is the best implementation for each cabinet but make use of all your inches-this is key for any slightly smaller kitchen.and definitely worth time spent figuring it out.

I've seen some comments that the roll-outs (I think you mean sliding shelves?) are handy for cookware specifically as the handles can overhang the sides, whereas with drawers the handles have to be tucked into the confines of the drawer because the sides are of course higher, and the handles themselves take up space in the drawer.
I think it would also depend on how large of a drawer you would have, if it's huge then handles likely would not be an issue.
We have 3 banks of drawers in our ~12x14 kitchen, and under the cooktop are 2 roll-outs which house our pans and pots. Opening the door and pulling out the shelf is not a big deal because we're not constantly pulling out pans every few minutes. But drawers for rest of the kitchen and those I would NOT want to be sliding shelves.
As is said so often and so wisely on GW, measure your stuff and get cabinets that accommodate.

In general- A)the advantage of rollouts would be they can be adjusted-B) you don't have a rail in between so there is some vertical gain in storage.
The disadvantage to roll outs is that you need to open the door first.

I often design in one cabinet with one rollout and 3-5 tray dividers. The rollout is kept towards the top of the opening. In frameless I can also get a shelf in there. The dividers are not just for trays but also for larger fry pans etc. There is often other tray storage in the kitchen (above fridge or oven). I like to make that cabinet 21" when I can so that it is a single door. I hate roll outs with two doors.

The other place I end up with rollouts is in wider pantries, which do have two doors. The vertical adjustment makes a big difference with groceries especially in a tall cabinet.

Drawers in framed cabinets- The way I prefer to set up pots and pans, nothing stacked on each other except colanders, a 3 drawer base in a framed cabinet suffers a bit. I often design with a 2 drawer preferably with the top drawer having a shallow drawer built into it.

Another option to look into are full pull out cabinets. These vary a lot by manufacturer but can give better overall storage per a space for certain types of items while adding convenience.

Aside from factory made ones, my current favorites are from Hafele. One with a metal frame and baskets, the other more recent they call SmartCab. That one is designed specifically for framed cabinets and for retrofit. Some of the options are good, some are too specific IMO. Best to keep it simple.

On occasions- when I can't get what I want from the factory for one of these things- I order a regular base cabinet with a door and drawer and two roll outs (WITHOUT soft close). Then I tell them not to attach the door or drawer. On framed we have to do the rest on site. The door and drawer are attached to each other, there are special pins available to do this. On framed we have to add a small piece of matching wood on the back at the space between the two. Then they are attached to the drawer box and the bottom roll out. The middle roll out is left loose and adjusted high enough to allow bottles to comfortably fit below it on the bottom roll out.

Jakuvall's "interior drawer in a drawer" gives you the best of both worlds.An adjustable interior rollout and a large fixed bottom drawer. It is very little work to pull out the interior drawer after the larger one opens, and they can be closed with one push. I think this is an ideal setup for pots with pot lids on the rollout above the pots.I don't think there is a difference in the square inches gained, just a difference in utility between rollouts and drawers.

roll outs are usually slightly narrower than drawers. They have to be that way to clear the hinges once the door is opened.

For my 21" pantry I chose rollout shelves, since I couldn't use a full pullout (next to wall, only one side accessible). This way I can open the door and see what is on all the shelves instead of opening drawer after drawer because I can't remember which one has the baking supplies.. Also, I will be able to add another one if I so desire.

Jakuvall, I want to add a drawer-in-drawer to my deeper utensil drawer -- right now I have an organizer stacked on top of another one with lesser used items. Have you seen an aftermarket one that can fit in a large (36") drawer? I saw something at Ikea that was a tray that slid back & forth on rails attached to the front & rear of the drawer, but that wasn't available separately; and I can't quite see how I can make one of their drawers work to do this. Since the drawer is already in, it would have to be something that fits inside the drawer box and not to the cabinet wall. These are frameless cabs. I'd appreciate any advice!

Jakuvall- your input is invaluable! I'm totally confused about something, though! I'm missing the point of the drawer-within-a-drawer. When or how is that better than two drawers in the same space? I'm getting closer to ordering cabs and I haven't considered them because I don't understand the benefits...