A320 has 3 levels of fly-by-wire redundancy "laws", Normal, Alternate and Direct, each with varying levels of protection. In Normal Law, "g", angle of bank and pitch protection would prevent aerobatic manoeuvers. When you begin to turn off flight control computers (or have failures) you end up in Alternate Law where most protections are lost (except load factor protection) This is the mode used in the sim for "unusual attitudes" and recovery, and it is definitely possible to roll the aircraft.
Cheers
DC