How can I group by multiple resources in kendo-scheduler without repeating entries?

Question

I'm using kendo-scheduler JavaScript component for a planning webapplication, and I'm doing a vertical grouping of an Employees resource; this way I get a row in the scheduler's timeline for each entry in Employees resource, and I can move/add events to/beetween each Employee's timeline.

group: {
    resources: ["Employees"],
    orientation: "vertical" },
resources: [{
    field: "employees",
    name: "Employees",
    dataSource: employeeResourceFromJSON }]

What I want to do now is add a new "Role" Resource, and use that for groping purposes too.

group: {
    resources: ["Role","Employees"],
    orientation: "vertical" },
resources: [{
    field: "employees",
    name: "Employees",
    dataSource: employeeResourceFromJSON },
{ 
    field: "role",
    name: "Role",
    dataSource: dataRole }]

The result is I get on the leftmost column a list of Roles, and for every role on the column immediately on the right each Employee is shown.

Is there a way to choose wich Employees resources are shown in the Role subgroup? I'd like to code a list of Employees for each role, and then show only the Employees with a specific role under that specific role subgroup but I can't seem to find a way to do this with KendoUI tools.

I tried filtering bu I couldn't come up with a statement that made sense :)