Once the API supports having multiple providers per encounter, the patientEncounters portlet used on the patient dashboard needs to display multiple values.
The initial implementation of this can just show a comma-separated list of provider names (and not show the encounter roles at all). Displaying the provider's name should be done through the <openmrs:format> tag. (This functionality may need to be added to that tag, if nobody has done it yet.)
A second pass could add a global property that controls what encounter roles are displayed in this column. This would allow an admin to have this column always show the attending physician, for example.
(It is not necessary to do the second pass while doing this ticket, but if you do not, please create another ticket for that when you complete the first pass here.)