The marching shoes of Roman soldiers (including Centurion) were caliga(e). Sandals made from three layers of cow-leather, a hard leather sole with supple leather strapping and toe/heel. They would be laced up to be tied on the shin or upon the ankle. Iron (or brass) hobnails would then be driven through the soles for added traction.

Now, the design is regarded to provide air-flow to the feet to help ward off blisters however blistering would be inevitable for any shoe of this time, for the length of the marches they would be subject to.

The reality is 'toughen up' would be the primary factor contributing to their marching ability, as it was with every marching army historically and in modern times. Humans are very adapt to long times spent on their feet with the body's natural reaction to repeated friction being calluses, which is hardened skin. So heavily callused feet would be crucial to a Roman soldiers' marching ability.

Aside from the air flow, the only other design features specific to the caligae to help combat blistering was the combination of supple leather and the number of straps. The leather straps would be tied tightly, with even pressure from all directions of the foot, up above the foot to the lower leg. In time the leather would mould to the shape of the foot somewhat and in combination with the added traction of the hobnails and being tied tightly, would leave a snug fit with very little, if not any, parallel movement between the sole of the foot and the shoe - the leading causes of blisters.

Source -----

Van Driel-Murray - Footwear in the north-western provinces of the Roman Empire 1985

Van Driel-Murray - The leatherwork from the fort 1998

Sparkes Hall - A history of boots and shoes