Roadmap unable to display cross Portfolio work

Issue Summary

On the Roadmap view, when you select multiple Portfolios it throws the "Only the first Portfolio in your selection will be used for filtering the work items in this view" warning.

Steps to Reproduce

1. Enter the Roadmap page;
2. Select more than one Portfolio in the tier 1 configuration.
3. Warning will appear

Expected Results

To have the ability to view more than one Portfolio work.
Customers have work that stretches across the portfolios so limiting the roadmap to only 1 portfolio at a time is making it very difficult for them to see a complete picture.
The warning displays "The Roadmaps can only be filtered by a single Portfolio, for the moment".

Actual Results

Only the first Portfolio in your selection will be used for filtering the work items in this view

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available