Reference Qualifier in Advance and Script Include in Servicenow(SNOW).

 On problem form, there should be a field problem owner ans user can only 

select those users in the field who has problem_manager role.

var prbFunctions = Class.create();

prbFunctions.prototype = {

    initialize: function() {},

    getprbmanagers: function() {

        var gr = new GlideRecord('sys_user_has_role');

        gr.addQuery('role', 'b573c1f9538823004247ddeeff7b12e0');

        gr.query();

        while (gr.next()) {

            var prbmanagers = prbmanagers + ',' + gr.user;

        }

        var result = 'sys_idIN' + prbmanagers;

return result;

    },

    type: 'prbFunctions'

};