walking can be described as a process of falling forward and catching oneself in a cycle. moving the root forward would be a good start - also you might want to tilt it a bit forward.

the arm might straighten out as it swings back. think of forward momentum. the best tool to work on a cycle in maya is the graph editor. obviously you have already been working with it but you might want to work more with the ideas of momentum and gravity in your head - eg. slowing the rise at the top and gathering speed in the fall, the impact of the foot hitting the ground and how that effects the rest of the body and in which order, how momentum effects limbs with joints like the leg and arm as they swing - the thigh swings forward and the shin reacts the opposite direction and as the thigh stops the shin/foot swing forward around the fulcrum of the knee. I'm not suggesting you should try and animate every one of these details but they are good things to keep in mind as you analyze the movement.

kurt's comment on the foot roll is right on - maybe think about the foot hitting the ground and then how it must change to conform to the ground as the body's weight passes over it on it's forward path.