Pattern fliers use to check the thrust by flying their models in a straight up line, if the model tends to go to the left then you need right thrust and vice versa. As has been noted I also would check the elevator halves to know if they move accordingly, the use of an incidence meter here is a must if we are thinking that the problem resides here. On some models like Cap and Sukhoi (to name just a few), at certain level of throw of the elevators the plane will tend to roll or even to snap (Do you have heard Snap-Cap?), so you have to be very careful on adding throw on any model and stick with the recommended throws by the manufacturer.