Turrets are superstructure mechanisms that rotate something (typically another mechanism) up to a full 360 degrees (or close - like 270 degrees, depending on if it includes a slip ring design).

Our team doesn't have the best experience with turrets and they're difficult to make in-house without complex machining but here are some resources:

Turn Table Bearings

Some teams who do not have access to a machine that can hollow out a sprocket or gear go invert belts directly onto a lazy susan/turn table bearing or attach a chain to it with special chain links like these from McMasterCarr. There are also teams who've made a turret through purely friction means.