those aren't enough variables to go on, just like velocity in a straight line, torque depends not just on the load but on the acceleration. Also, in the case of rotational forces and accelerations you have something called moment of inertia, it's an exponential average of the mass and its distance from the center of rotation. Because weight at a greater distance from the center takes more force (torque) to accelerate.
This is the formula for moment of inertia. Don't worry if you don't know calculus, they have derived forms for different shapes. r is the distance from center at every point, and dm refers to the mass at each point.
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This is a list of derived moments of innertia for basic shapes
List of moments of inertia - Wikipedia, the free encyclopedia
The units come out in mass*length^2, but this is ok, because torque is moment of inertia times angular acceleration
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which has units of seconds^-2
so when you multiply them you get mass*length^2*seconds^-2
force is mass times acceleration, acceleration is length*seconds^-2 so if we pull force out of the above equation we get, length*force, aka foot lbs, or newton meters, torque.
Edit: I see you posted while I was typing, I guess the first reply was right in asking first. For propelling something you are mainly considering F=ma. but if you want a simple solution just push the thing at the speed you and estimate the force, multiply that by your wheel radius and there's your torque. Any gear ratios will divide the speed and multiply the force, or vise versa.