static void assignRole(ManagementAPI api) {
    try {
        api.organizations().addRoles(ORG_ID,
            USER_ID,
            new Roles(Arrays.asList(ADMIN_ROLE_ID)))
            .execute();
    } catch (Auth0Exception e) {
        e.printStackTrace();
    }
}

static void listInvitations(ManagementAPI api) {
    try {
        // Originally failed when invitation contains one or more Roles
        InvitationsPage page = api.organizations().getInvitations(ORG_ID, null).execute();
        for (Invitation i : page.getItems()) {
            System.out.println(i);
        }
    } catch (Auth0Exception e) {
        e.printStackTrace();
    }
}

static void sendInvitation(ManagementAPI api) {
    Invitation invitation = new Invitation(
        new Inviter("Luciano"),
        new Invitee("[email protected]"),
        CLIENT_ID
    );
    invitation.setRoles(new Roles(Arrays.asList(ADMIN_ROLE_ID)));
    Invitation result;
    try {
        // Originally failed because invitation contains one or more Roles
        result = api.organizations().createInvitation(ORG_ID, invitation).execute();
        System.out.println(result.getInvitationUrl());
    } catch (Auth0Exception e) {
        e.printStackTrace();
    }
}