No reason why there needs to be a character friend list then a roster friend list
I think that might be coming our way in the future. If im not mistaken a patch for the korea version removed the character friends list, so there is only the roster friends list.
It also allowed them to make cross server roster friends and invite cross server friends into their stronghold.
I think this was announced in the roadmap for the next big update.
oh nice!
Yes there will also be a new friendlist where you can add friends from other servers. I don’t know exactly when they intodruce that
I just wonder. There is already a roster friendslist. You actually need to add the character friend first then you can request to be a roster friend. But it is actually already implemented in the game. 
Additionally you can use a seperate chat room (top left speak bubble) for your (roster) friends or guild (like i already have with RL friends and my guild because many people have alts in different guilds etc).