This paper proposes a novel methodology for the design of series elastic actuators in parallel-actuated platforms which have full six degrees-of-freedom in position and orientation. Series elastic actuators can potentially contribute to lower power consumption and provide a better human-machine interface for the user. This is an important consideration in the use of a robotic spine exoskeleton for human subjects, which motivates this work. In the study of parallel-actuated systems with full six degrees-of-freedom, the effect of compliance in series with actuators has not been adequately studied from the perspective of kinematics and wrench capabilities. These analyses are performed in this paper with the goal to improve the design of the robotic spine exoskeleton (ROSE) and its human usage.