Currently there is no way to adjust the hours from week to week for unassigned roles within the workload balancer. The balancer evenly spreads the planned hours over the duration (not evenly sometimes), but you cannot adjust them to meet the actual cadence of work.
As an example, if you have 40 hours with a duration for 10 days (2 weeks). The balancer will spread that as 20 hours the first week and 20 hours the second week. We should be able to adjust that so it is 30 hours the first week and 10 the second (or whatever the correct number would be).
It should be the same functionality as working with the assigned resources.