Import a set of system roles to assign it to an user

If this is a one-time action then you don't need to use sync tool.
one simple way of doing this...

Step 1:
Use the Object Browser make a query for collection all the UID or XObjectKey data
and account, roles names for matching things up.

Ex:
select centralaccount, uid_person from Person
(right click export to CSV person.csv)
select ident_eset, uid_eset, xbojectkey from eset
(right click export to CSV eset.csv)

Step 2:
Add this to the assigments csv (excel, powershell)

Ex:
centralaccount, uid_person ident_eset, uid_eset
user01, 1234-..., Role03, 4321-...
user01, 1234-..., Role03, 4321-...

Step 3
User the Data importer (in Launchpad)
The GUI is pretty self explanatory
select PersonHasEset as import table

Thanks Niels de Groot  for your answer. 

As it's one-time action, your solution is appropried.

I wandered, howover, if OIM don't has a way to do that without we use a script ?

Without any scripting... just a little sql

You could create a custom table with columns identical to the csv file.
Use the Data importer import csv in custom tables.
Build your sql query (join the required tables)
Export the required UID, XObjectKey columns to csv
Use the Data importer import this csv in the assignment table.

Thank you Niels de Groot