The classis signs of RTS are the loss of cyclic control, usually a gradual thing (because RTS is a gradual thing) where the lateral cyclic trim (where the cyclic needs to be to keep the wings level) begins to move rapidly toward the retreating side. This is accompanied by some increase in n/rev vibration, usually. Eventually, the cyclic hits the stops and the aircraft rolls toward the advancing side. At the same time, the nose tries to lift, so the cyclic needs to go somewhat forward. The reason why the aircraft behaves assymetrically, as compared to airplanes, is that the rotor is losing lift on one side only.