Scott:
I am sure that others will chime in here, but the short answer is, yes, you want your cockpit/seat/footbraces to fit you well before learning rolling and advanced bracing. The only way to go from paddling "in a kayak" to paddling "with a kayak" is to have it fit you well. "Well" encompasses a lot of things.

First and foremost, your boat needs to be comfortable. If it hurts to be in the boat, you won't want to spend the time in it that you need to practice and improve. Your seat should be comfortable and provide the level of back support and under-thigh support that you need to spend time in the boat comfortably. Comfortable also means that you are confident that you can get in and out of the boat when you need to.

Next, your boat needs to fit your body. Footpegs or braces need to allow you to brace your knees/thighs under the deck without slipping and hip pads or cheekplates need to keep your butt reasonably centered and your hips locked in. If you cannot get purchase with your hips and knees, you will have a heck of a time with rolling, edging and bracing.

The upside is that you can adjust the fit of your cockpit with various bits of minicell foam, neoprene, etc. It is not hard, does not take an excessive amount of time and does not require, in most cases, massive modification to the boat. For my Great Auk, I had a seat made by Joe Greenley or Redfish Kayaks (www.redfishkayak.com). It takes care of the comfort and hip pad aspects and slips in and out of the boat for cleaning. I also padded the underside of the deck where my knees hit with "grippy" neoprene (old mouse pads) so that my knees don't slip out when I brace against them while wearing my wetsuit.

My 2­¢

Marcel