The Roman Legion, like most organized armies throughout history had a very distinguished awards system. Decorations were usually worn by the soldiers on parades and were generally awarded at the end of a campaign or could be added to the eagle standards for entire units.
The following are some of the known awards in order from least to most important:
Torques A minor rank & file decorations for valor worn around the neck.
Armillae Another rank & file minor decoration for valor worn as an armband.
Phalerae A third type of rank & file decoration was an embossed disc, worn on the uniform.
Corona Aurea (Gold Crown) Awarded to both Centurions and apparently some principales, for killing an enemy in single combat and holding the ground to the end of the battle
Corona Vallaris (Fortification) Was made of gold and decorated with the uprights (valli) of an entrenchment. It was awarded to the first soldier or Centurion to force his way into an enemy's palisade.
Corona Muralis (Wall) Was made of gold and decorated with turrets. It was awarded to the first soldier or Centurion who got over the walls and into a besieged city.
Corona Civica Was made of oak leaves and acorns. It was awarded to a soldier who saved another's life in battle: "To have preserved the life of a Roman citizen in battle, slain his opponent, and maintained the ground on which the action took place." An extraordinary award, it brought many social privileges thereafter for the soldier's lifetime.
Corona Graminea (Grass) or Obsidionalis (Siege) The rarest of honors, was given to a Legate who broke the siege of a beleaguered Roman army. The wreath was made out of grasses gathered from the site where the siege had been lifted. It was presented to the general by the army he had rescued.
Other awards given strictly to officers and seemed more likely to be ceremonial as a recognition of a term of service rather than for some act of valor:
Hasta Pura Was a spear, possibly with a silver shaft, but without the iron tip for use in combat. Was awarded to the Primus Pilus possibly upon completion of service.
Vexillum This award was a little miniature standard mounted on a silver base.