How to display a custom message in keycloak login page if no roles assigned user tries to login

Question

I have a spring boot application implemented with keycloak security so i want to display a error message when a user having no roles tries to login
I have this login.ftl page

<#import "template.ftl" as layout>
<@layout.registrationLayout displayMessage=!messagesPerField.existsError('username','password') displayInfo=realm.password && realm.registrationAllowed && !registrationDisabled??; section>
    <#if section = "header">
        ${msg("loginAccountTitle")}
    <#elseif section = "form">
    <div id="kc-form">
      <div id="kc-form-wrapper">
      <marquee behavior="scroll" direction="left" scrollamount="5">
    This is a scrolling text using the marquee tag.
</marquee>
        <#if realm.password>
            <form id="kc-form-login" onsubmit="login.disabled = true; return true;" action="${url.loginAction}" method="post">
                <#if !usernameHidden??>
                    <div class="${properties.kcFormGroupClass!}">
                        <label for="username" class="${properties.kcLabelClass!}"><#if !realm.loginWithEmailAllowed>${msg("username")}<#elseif !realm.registrationEmailAsUsername>${msg("usernameOrEmail")}<#else>${msg("email")}</#if></label>

                        <input tabindex="1" id="username" class="${properties.kcInputClass!}" name="username" value="${(login.username!'')}"  type="text" autofocus autocomplete="off"
                               aria-invalid="<#if messagesPerField.existsError('username','password')>true</#if>"
                        />

                        <#if messagesPerField.existsError('username','password')>
                            <span id="input-error" class="${properties.kcInputErrorMessageClass!}" aria-live="polite">
                                    ${kcSanitize(messagesPerField.getFirstError('username','password'))?no_esc}
                            </span>
                        </#if>

                    </div>
                </#if>

                <div class="${properties.kcFormGroupClass!}">
                    <label for="password" class="${properties.kcLabelClass!}">${msg("password")}</label>

                    <input tabindex="2" id="password" class="${properties.kcInputClass!}" name="password" type="password" autocomplete="off"
                           aria-invalid="<#if messagesPerField.existsError('username','password')>true</#if>"
                    />

                    <#if usernameHidden?? && messagesPerField.existsError('username','password')>
                        <span id="input-error" class="${properties.kcInputErrorMessageClass!}" aria-live="polite">
                                ${kcSanitize(messagesPerField.getFirstError('username','password'))?no_esc}
                        </span>
                    </#if>

                </div>

                <div class="${properties.kcFormGroupClass!} ${properties.kcFormSettingClass!}">
                    <div id="kc-form-options">
                        <#if realm.rememberMe && !usernameHidden??>
                            <div class="checkbox">
                                <label>
                                    <#if login.rememberMe??>
                                        <input tabindex="3" id="rememberMe" name="rememberMe" type="checkbox" checked> ${msg("rememberMe")}
                                    <#else>
                                        <input tabindex="3" id="rememberMe" name="rememberMe" type="checkbox"> ${msg("rememberMe")}
                                    </#if>
                                </label>
                            </div>
                        </#if>
                        </div>
                        <div class="${properties.kcFormOptionsWrapperClass!}">
                            <#if realm.resetPasswordAllowed>
                                <span><a tabindex="5" href="${url.loginResetCredentialsUrl}">${msg("doForgotPassword")}</a></span>
                            </#if>
                        </div>

                  </div>

                  <div id="kc-form-buttons" class="${properties.kcFormGroupClass!}">
                      <input type="hidden" id="id-hidden-input" name="credentialId" <#if auth.selectedCredential?has_content>value="${auth.selectedCredential}"</#if>/>
                      <input tabindex="4" class="${properties.kcButtonClass!} ${properties.kcButtonPrimaryClass!} ${properties.kcButtonBlockClass!} ${properties.kcButtonLargeClass!}" name="login" id="kc-login" type="submit" value="${msg("doLogIn")}"/>
                  </div>
            </form>
        </#if>
        </div>

    </div>
    <#elseif section = "info" >
        <#if realm.password && realm.registrationAllowed && !registrationDisabled??>
            <div id="kc-registration-container">
                <div id="kc-registration">
                    <span>${msg("noAccount")} <a tabindex="6"
                                                 href="${url.registrationUrl}">${msg("doRegister")}</a></span>
                </div>
            </div>
        </#if>
    <#elseif section = "socialProviders" >
        <#if realm.password && social.providers??>
            <div id="kc-social-providers" class="${properties.kcFormSocialAccountSectionClass!}">
                <hr/>
                <h4>${msg("identity-provider-login-label")}</h4>

                <ul class="${properties.kcFormSocialAccountListClass!} <#if social.providers?size gt 3>${properties.kcFormSocialAccountListGridClass!}</#if>">
                    <#list social.providers as p>
                        <li>
                            <a id="social-${p.alias}" class="${properties.kcFormSocialAccountListButtonClass!} <#if social.providers?size gt 3>${properties.kcFormSocialAccountGridItem!}</#if>"
                                    type="button" href="${p.loginUrl}">
                                <#if p.iconClasses?has_content>
                                    <i class="${properties.kcCommonLogoIdP!} ${p.iconClasses!}" aria-hidden="true"></i>
                                    <span class="${properties.kcFormSocialAccountNameClass!} kc-social-icon-text">${p.displayName!}</span>
                                <#else>
                                    <span class="${properties.kcFormSocialAccountNameClass!}">${p.displayName!}</span>
                                </#if>
                            </a>
                        </li>
                    </#list>
                </ul>
            </div>
        </#if>
    </#if>

</@layout.registrationLayout>


and this is my config class 

@Configuration
@EnableWebSecurity
public class KeycloakSecurity extends KeycloakWebSecurityConfigurerAdapter {

    @Bean
    @Override
    protected SessionAuthenticationStrategy sessionAuthenticationStrategy() {
        return new RegisterSessionAuthenticationStrategy(
                new SessionRegistryImpl());
    }

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        super.configure(http);
        http.authorizeRequests()
                .antMatchers("/dashboard").hasAnyRole("Employee", "Manager")
                .antMatchers("/logout").permitAll()
                .anyRequest().permitAll()
                .and()
                .formLogin()
                .successHandler(successHandler()) // Set custom success handler
                .and()
                .csrf().disable();
    }

    @Autowired
    public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception {
        KeycloakAuthenticationProvider keycloakAuthenticationProvider = keycloakAuthenticationProvider();
        keycloakAuthenticationProvider.setGrantedAuthoritiesMapper(new SimpleAuthorityMapper());
        auth.authenticationProvider(keycloakAuthenticationProvider);
    }
    @Bean
    public AuthenticationSuccessHandler successHandler1() {
        return new SimpleUrlAuthenticationSuccessHandler() {
            @Override
            protected String determineTargetUrl(HttpServletRequest request, HttpServletResponse response) {
                Collection<? extends GrantedAuthority> authorities = SecurityContextHolder.getContext().getAuthentication().getAuthorities();
                List<String> roles = authorities.stream()
                        .map(GrantedAuthority::getAuthority)
                        .collect(Collectors.toList());

                System.out.println("User successfully authenticated. Roles: " + roles);

                // You can add logic to check for roles here
                // For simplicity, assume no roles for now
                return request.getContextPath() + "/noRoles";
            }
        };
    }
}

if i change anyting in this i am getting internal server error in keycloak

I tried in this way

<#if !authentication?.account?.roles?has_content> You don't have any roles. Please contact the administrator for assistance. </#if> but I am getting this error

   Failed to load resource: the server responded with a status of 404 (Not Found)

auth:1 Refused to execute script from 'http://localhost:8080/resources/1gs7r/login/keycloak%20-%20Copy/js/script.js' because its MIME type ('') is not executable, and strict MIME type checking is enabled.