Riverine environments: Long single handed rods, greater than nine feet in length, in a 7 or 8 weight fished with a long bellied line like a steelhead taper are great for mending line. Excellent line control is required for nymphing areas of complex currents like riffle sections. It will also help with increased casting distance to reach distant lies that are holding fish. Fish heavy flies. You may need to adjust the weight needed to reach bottom by adding split shot to your leader. Think steelhead tactics.
The two handed rod or a switch rod can be very effective tools when fishing in this manner. I prefer a 7 weight switch rod or a shorter fast action 5 weight spey rod fished with Skagit tapers and polyleaders. They are nasty for casting way out there and reaching fish unobtainable to most other anglers.
For high flow/heavy current situations, a 9 or 10 weight rod may be desired to steer/turn fish from running downstream.
Roughfish will require a stout reel. A reel with a good disc drag (or conical drag like the Lamsons) and room for ample backing is mandatory gear. Though you may not typically need more than 100 to 150 yards of backing, there may the occasional rogue fish who will decide to take you to your spool.
Lacustrine environments: A standard fast action nine foot rod in a 6 through 8 weight will get the job done. When fishing a lighter rod like a 6 weight, look for a saltwater or steelhead/salmon version that comes equipped with oversized rod guides and a fighting butt. You will find those features comforting. A quick loading line will help you get off quick casts to fish cruising on the flats. A fine to moderate presentation is often required; it may be worth looking in to a bonefish or redfish line when fishing warmer climates, since there are not many carp specific lines that are currently commercially available. An intermediate sink line may be helpful in keeping your line below the surface in choppy weather.
Like in the river environments, a good disc or conical drag is required when fishing for roughfish in lakes. A moderate to high amount of backing may be required; a minimum 150 to 200 yards of backing is compulsory, especially when fishing the flats of the Great Lakes. Many of the same gear suited for bonefish will fit the bill for lacustrine carp.