Rorn does not have many forests. The climate of the northern half of Aurepos ends up actually being fairly arid, as the mountains cause a rain shadow.
Rorn currently has a number of feudal lords battling for control. There has not been a high king for many decades.
What lies north of the Jutting Mountains is up to you. It hasn’t been defined in the canon. At some point in the distant past, the various human and elven peoples of Aurepos immigrated from there, and more recently the Jutlandic peoples came from there. In my “head canon” (unpublished) there is something evil up there that the Jutlanders were fleeing, but no published etails.
No, Rorn has been largely undeveloped. I’ve shared info on it from time to time on the forums and discord.