Roger - thanks for 'chiming in" but I'll answer it anyhow even though Gary did his edit

Gary - for a grocery getter engine, you probably wont see much of a difference. Add a little more camshaft, you will see some help. Roller rockers are just that. The aluminum after market versions will add rollers at the trunnion as well as the valve tip end instead of friction/sliding action in those places. Also, they supposedly run cooler. Now, the big advantage to this particular set is that instead of being the standard Ford 1.6 which translates to my particular camshafts lift as .498, the 1.7 roller rockers - those valves will now open to about .530 lift - an inexpensive performance adder. Supposedly it will work to improve the actual camshaft overlap - but I really kinda doubt that. As far as my car, reverting back to 1.6 ADJUSTABLE rockers has taken the edge off the idle speed(better), the exhaust note(worse) as will as the seat of the pant feel(not as good). BUT they are a PITA to adjust preload on, at least my engine as I would have needed longer, custom built push rods. See my long winded thread for that story.

Most other folks, according to another Ford related website, 'love' these rockers