Smaller diameter rockets have similar to somewhat less ranges when compared to tube artillery. Launching racks are simple and are typically truck mounted. Diameters are around 115mm to 122mm. They are an imprecise area weapon usually fired in large quantities which can be effective for saturating an area with explosives. Their use is mostly favored by Russia and some ex-Soviet or other aligned countries.
Large quantities of the 9M22U,
122mm rockets, nicknamed GRAD which means hail, are being used in the war in Ukraine. Mainly used by Russia, the GRAD is 9'-5" long, has a range of 12.6 miles and a 41 pd explosive charge. The museum and store have INERT examples including cut-a-ways on display and for sale.
Larger artillery rockets...
Larger rocket artillery is around 250 to 300mm in diameter and larger. They have much longer range than tube artillery, are more accurate compared to smaller rockets, or can be ultra precise.
They also have a much larger payload compared to any other current artillery. These rockets are significantly more expensive. In addition, the launch vehicle is sophisticated and the whole system requires skilled, well trained crews. The advantage to the larger, highly accurate rocket systems is generally the USA, NATO, and Allied Forces.