There are two kinds of roller rockers, there are adjustable and non adjustable. The non adjustable rockers are cheaper. When installing adjustable ones you will need to adjust them up to the right pre load. The adjustable ones usually require some shimming. The give you more lift and move more smoothly than stock rocker arms. They are not very hard to install though. They won't make a noticable difference on a stock car, with a cam though they make a big difference. Here is a link to the install instructions for them:greenfieldracin said:
http://www.supersixmotorsports.com/PDF/AdjustableBilletRollerRockerInstallation.pdf