Rollers available in many widths, diameters, gauges and capacities. Most common is steel-zinc plated, but available also in stainless and plastic. Fixed or adjustable height stands available.
Single line and double line wheel tracks are commonly used to transport palletized goods -- capacity and pitch will depend on load and pallet board orientation.
Skate wheels are an option to rollers, and when they are close coupled (40 mm pitch), make an ideal transfer conveyor for sacks. Picture shows skate wheels at 80 mm pitch.