Here is the full list of all 21 War of the Roses achievements.
Reach rank 1.
Finish as the best player in a ranked match.
Finish 2nd in a ranked match.
Finish 3rd in a ranked match.
Obtain all Mounted prizes.
Obtain all weapon efficiency prizes.
Obtain all support efficiency prizes in the game.
Obtain one of each prize in the game.
Reach rank 7.
Reach rank 13.
Reach rank 20.
Reach rank 25.
Reach rank 30.
Reach rank 40.
Reach rank 50.
Reach rank 60.
2001 crossbow headshots.
Gain 10000 XP in one round.
Kill 10 enemies in a row.
Hit an enemy with a ranged weapon from ~160 feet.
Keep the war civil and serve an english breakfast to your favoured foe.