If the C/O ratio in graphite oxide is low (~ 2), the material is non-conductive which could explain why you get a CV typical for ohmic resistive materials.
If the electrode's characteristic is mainly influenced by a high resistance, Ohm's law (E = R * I) applies for the electrode. As the resistance (R) is constant, you get a linear increase in current (I) with rising potential (E). The slope of the linear line is the resistance. Therefore, the observed current is only dependent from the resistance of the electrode. On the other hand, i would not use this kind of technique to determine the resistance of the material as the errors by using this kind of setup might be very high.