what is your intention of backing up like this? I mean here you gonna backup user files and then some system files? and about that folders, the are not the same, one contains the data(downloaded emails, other one is acting like a temp folder for the email like if you use IDM, unfinished downloads will be in roaming/IDM.and roaming folder mostly involves with things hapening while you're connected to the internet. I dont know about it much but some expert here will explain.
and again, what do you expect by backingup like this, is it for, recovering your system as it is now if something goes wrong or just to keep your files for later use?