AC Rogue The main game of the series or an offshoot??? (Assassin's Creed: Unity)

Can you please tell me AC rogue is the main game of the AC series or an offshoot? Thanks in advance :)
PS I consider the main games: ac 1, ac 2, ac brotherhood, ac revelation, ac 3, ac 4 black flag, ac unity, ac syndicate.
PPS If something is wrong, please correct me.