Some line rollers have one or two ball bearings inside. On cheaper reels, there will be a simple bushing instead of bearings. In either case, undo the little screw or nut that holds the bail to the rotor arm, thereby freeing the line roller. Clean the inside of the roller and the bushing/bearings with a light solvent, then add no more than one or two drops of oil. Reassemble, making sure the line roller moves freely, and you're good to go for another year.