Is there a time difference between two points at the same longitude but at different latitudes?
Earth's rotation has a fixed angular speed, therefore time is the same across the entire surface.

Even though the tangential speed (speed of the point in the surface) is different in each place of the surface, what counts here is the angular speed (the speed of rotation). Different tangential speed compensate the distance to the rotation axis by:

(angular speed) = (tangential speed)/(distance to axis)