multiple roles for a user ?

Is it possible to give multiple roles to the same user?

for example :
1. a general role "RoleA" for most users, for "grants and revokes" on certain tables and certain columns.

2. plus a role "Role_user" particular for each of them for its additional personal access
 with "grants" and "revokes" on other tables and columns.

Thanks.
Regards.

Etienne DECHERF
SOPRA STERIA
for APHP Paris