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