In armies throughout the ages, the marching boot has been a prized possession. Weapons will only be needed in times of war, but the boot is needed every single day. Command sends the soldier into awful terrain on a regular basis, for long periods of time, often to cover very large distances.
And as has been stated in other answers, earlier legionaries wore the caligae, open sandal-like boots that had thick soles held together with hobnails. From the late 1st century onwards the army began to equip itself with calcei, an enclosed boot more often used by civilian workers. This transition may reflect the fact that more recruits were coming from the northern frontiers, where enclosed boots are of great benefit, or it might reflect changes in the supply system, with legions turning to civilian sources for their footwear. Whatever the reason, calcei were ubiquitous in the British provinces. At Vindolanda a Roman fort on Hadrian’s wall, the wet conditions have preserved many examples of Roman footwear, civilian and military, adult and child. A great proportion (of all types) have hobnails hammered into the soles, a technique which binds the thick soles strongly together, which reduces wear and tear, and which gives an excellent grip akin to wearing modern football boots!
These are a pair of reproductions worn by a reenactment legionnary, who had them for three years.
Credit : Quora
Picture Credit : Google