The paper presents a creative design approach focused at simplifying the control of biped humanoid robots locomotion in a domestic scenario. The creative design approach is the result of intensive studies aimed at optimizing dynamic balance ZMP-based control on fully-actuated biped platforms. The innovative solution proposed in this paper is applied to the realization of a novel humanoid robot, ROLLO, which is based on the implementation of a passive flexible structure constituting the robotic legs, and of wheeled feet. The unconventional use of the cylindrical helical springs in the flexible structure of the legs allows obtaining a biped robot able to achieve an alternate leg motion having only two active motors and remaining in a standing position also when the motors are not active.