No. Once a retreated army has been routed, it can longer add to the combat strength of a region. It could still "participate" in combat, but it would be pointless. If they are forced to retreat again, they are destroyed.
Not always pointless: a Baratheon footman, who routed into an area with a support order, can support +0 in a battle. If the Baratheon player uses the Renly Baratheon card and wins, the routed footman can be upgraded to a Knight (see FFG official answers thread).
To answer original poster: in the turn in which they have been routed, they can no longer move.