Here is the full list of all 21 War of the Roses achievements.
Reach rank 20.
Gain 10000 XP in one round.
Reach rank 13.
Kill 10 enemies in a row.
Finish as the best player in a ranked match.
Finish 3rd in a ranked match.
Finish 2nd in a ranked match.
Reach rank 7.
Hit an enemy with a ranged weapon from ~160 feet.
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.