Take it apart, clean it really well, replace the rollers if necessary (if they have divots worn in them), i dont think the ball itself makes much difference (unless its not smooth)
Try to reuse the bearings if possible, if not get replacements (unsealed), either way clean all the grease out of them with degreaser, clean with alcohol, and if possible run them as fast as you can with a power tool for as long as you can... Basically break them in, you want themto be as free spinning as possible... When they run well add a little light lube, or just leave them dry