Could anyone clear up the event up of Chapter 2 (Roche's path) for me?

1) He conspired against King Henselt in the hope that he could get enough of the nobles to rebel and overthrow Henselt. This would then let King Foltest (the king that Roach served) invade and conquer large portions of Kaedwen. The plan was made several years before the events of Witch2 but put on hold because of other things happening and Roach is only know getting back to it.

2)The battlefield curse activated because of several things happening. A comet appearing in the sky, King Henselt's only son being killed, a conspiracy forming against him and the death of an innocent holy man. These were all specifically events that needed to happen for the curse to be activated. The curse itself is for all the soldiers who died in a previous war to come back as undead specters and to fight for all eternity in a slowly expanding fog that will eventually cover the world.

3)This can be a little confusing because the soldiers talk about 2 major wars. The first was 6 years before Witch2 and against another country called Nilfgaard that was invading the Northern Kingdom. That war involved all the Northern Kingdoms (including Kaedwen) as a united front against the Nilfgaard's and the Northern Kingdoms won. The second war (the one the curse is about) happened 4-3 years before wicth2 and was between 2 Northern Kingdoms Kaedwen and Aedirn. This war happened because Kaedwen (ruled by Henselt) invaded and tried to conquer Aedirn however there was no clear winner as both sides suffered very heavy losses with no clear gain. Now (during witch2) Henselt is invading Aedirn again.

4)Sabrina was a sorceress and the adviser of King Henselt (they never got on at the best of times) and during the war between Kaedwen and Aedirn she cast a spell that made giant fireballs rain down from the sky which decimated both army's. Henselt was enraged by this and ordered her burned at the stake. It was while she was being burned that she laid the curse upon Henselt. That he would be the last of his bloodline, that he would never conquer Aedirn and that he would die. When the curse was activated the fog full of dead soldiers made it impossible for Henselt's army to march into Aedirn.