Yes, routed units cannot do anything on their own, and will "run away" with more losses and morale hits. If they are stacked with a non routed unit, they will stay in place. On their next turn, if isolated, and they don't pass a "morale" check (not sure what it is, and don't feel like trying to find it atm), they will surrender before you can do anything. If they pass the check, they will be on the map, just waiting for you to go up and attack them.
I find in what I would call more advanced play, you can watch the way they route, which is towards an HQ, and pretty well "herd" a big group of units in that direction. The hardest part is moving in a big enough encirclement so they stay in place and you get easy surrenders.