I bet it's specific to whoever gave the Geass. The Emperor and Rollo's geass are probably more stable than CC's. Mao and Lelouch's geass went out of control pretty fast, CC seems to have abandoned Mao shortly after giving him his geass.
Also, Lelouch's Geass only works when you give them verbal orders. Like his stupid "kill all Japanese", it was a specific verb to trigger obedience. He chose his words well while talking to Rollo and didn't give tell him to do anything specific.