Well, temperature will play around with the Mobility (falls with the temperature), the threshold voltage ( increases with the temperature), the doping concentration ( reduces with the temperature). If you look into your GBW and gain,
GBW = gm/CL where gm= un*Cox*(W/L)*(VGS-VTH)
gain = gm*ro where ro= 1/lambda*ID
Since ID and gm fall down with the temperature, your gain and GBW also tend to fall down.