This.
I have a roll up and its way better than the snaps or the fold up ones. All you do is unroll it, and latch it at the end (the mechanism basically stretches itself, adjustable tensioners) and then you run your hands down the side over the velcro, done. Open bed to sealed in less than 30 seconds.
I have the LUND brand cover linked here (this website is pretty awesome too, they will price match anything), oh yeah bonus is the lifetime warranty.
http://www.truckaddons.com/Catalog/subpages/Lund_genesis_rollup_cover.htm
Do yourself a favor and don't get a plastic liner. It will just get crap built up under neath it...wear off the paint at the contact points and start rusting. Full of fail.
They have great floor mats and stepbars and whatever you want.
Depending on the truck, the 03 and up Ram Factory bars are stainless I believe.
They also price matched me a $200 brake controller at $100. I believe its the tekonsha prodigy.