rollers are easier on parts, less oil temp, less friction, easier starting, better gas mileage, and most importantly more HP/torque. Down side is they are a bit expensive and a bit noisier than factory rockers, which most of us hotrodders dont mind a bit of noise
I doubt if you will gain much HP by using roller rockers. The real gain as mentioned above is the reduced strain/loads/wear/friction/etc on the valve train. You are converting the cam/lifter/pushrod direction/motion approximately 180 degrees against, in some cases, considerable valve spring pressure.
I just fired up my new engine with roller rockers and it has what I would call slightly loose rocker noise should I be adjusting this out or is this the noise of which you fellas are speaking? If I had normal rockers they sound like they need another 1/4 turn tightening.
Rollers should NOT make excessive noise. If you are getting clatering and ticking, you should be able to adjust it out if the cam is hydralic.
The 5.0L Cobras came from the factory with roller rockers. I've never heard any one complaining about noise.
I remembered this thread as I was reading Hot Rod last night. In the latest issue, they do a series of bolt ons on a Mopar 360, testing after each change. Roller rockers gained about 3 HP and about 3 LBFT at the rear wheels over stock, and they went up a ratio (1.5 to 1.6).