Get Login User Role name in JavaScript using OData

//Check login User has 'System Administrator' role

function CheckUserRole() {

    var currentUserRoles = Xrm.Page.context.getUserRoles();

    for (var i = 0; i < currentUserRoles.length; i++) {

         var userRoleId = currentUserRoles[i];

    var userRoleName = GetRoleName(userRoleId);

        if (userRoleName == "System Administrator") {

            return true;

        }

    }

    return false;

}

//Get Rolename based on RoleId

function GetRoleName(roleId) {

    //var serverUrl = Xrm.Page.context.getServerUrl();

    var serverUrl = location.protocol + "//" + location.host + "/" + Xrm.Page.context.getOrgUniqueName();

    var odataSelect = serverUrl + "/XRMServices/2011/OrganizationData.svc" + "/" + "RoleSet?$filter=RoleId eq guid'" + roleId + "'";

    var roleName = null;

    $.ajax(

        {

            type: "GET",

            async: false,

            contentType: "application/json; charset=utf-8",

            datatype: "json",

            url: odataSelect,

            beforeSend: function (XMLHttpRequest) { XMLHttpRequest.setRequestHeader("Accept", "application/json"); },

            success: function (data, textStatus, XmlHttpRequest) {

                roleName = data.d.results[0].Name;

            },

            error: function (XmlHttpRequest, textStatus, errorThrown) { alert('OData Select Failed: ' + textStatus + errorThrown + odataSelect); }

        }

    );

    return roleName;

}