Lathrup Industries offers a large variety of rollers including Gravity rollers.
Available in sizes from 1" DIA to 6" DIA. Round axles are available in 1/4 " to 3 7/16" DIA. Hex axles are available from 5/12" hex to 1 1/2". Many bearing options are available as well as a variety of coatings and sleeves, such as urethane, ultrex, electorplating, and knurling.
Power Rollers with sprockets
These are similar to gravity rollers, using "A" plate sprockets welded to tubes or shafts for use in Chain Driven Live Roller Conveyors. Various sizes of sprockets are available RC-40 to RC-120.