Basically yes. Generated torque is proportional to current (in Ampere). Output torque at the shaft will be somewhat less than predicted at increasing speed due to internal drag and electric losses.
And speed (RPM) is proportional to voltage. The same applies here, at higher speeds there will be some losses. So it's not linear ad infinitum.
Below rated speed for all practical purposes you can regard output torque and speed to be directly proportional to current and voltage. Above that the losses will get into play. So will electric factors related to the fact that the motor have coils, and thus have an inductance. And.... Well let's say it's best to keep below rated isn't it?
