First of all you should not go directly to login.jsp.
You just call a protected page (protected by <security-constraint> element ) and Tomcat (web server of jboss) will first  call login.jsp to perform authentication and if it is succesful will load protected page. In this page you can check then user roles and forward to necessary URL based on role.

Let illustrate it with an example.
So you have following directory structure in your webapp:
/
-login.jsp
 protected/
 protected/firstpage.jsp
 protected/admin/...
 protected/usualuser/....

in your web.xml you add following:
---
<web-app>
....
<security-constraint>
        <web-resource-collection>
              <web-resource-name>Sample Application</web-resource-name>
              <description>Require users to authenticate</description>
              <url-pattern>/protected</url-pattern>
              <http-method>POST</http-method>
              <http-method>GET</http-method>
        </web-resource-collection>
        <auth-constraint>
            <role-name>admin</role-name>
            <role-name>others</role-name>
        </auth-constraint>
            <user-data-constraint>
                  <transport-guarantee>NONE</transport-guarantee>
            </user-data-constraint>
      </security-constraint>
      <security-role>
            <description>admin users</description>
            <role-name>admin</role-name>
      </security-role>
      <security-role>
            <description>Other users</description>
            <role-name>others</role-name>
      </security-role>
      <login-config>
            <auth-method>FORM</auth-method>
            <form-login-config>
                  <form-login-page>/login.jsp</form-login-page>
                  <form-error-page>/login.jsp</form-error-page>
            </form-login-config>
      </login-config>

...
</web-app>
---

In your firstpage.jsp you do checkup user roles and based on that forward to necessary URL:
<%if(request.isUserInRole("admin")){%>
        request.forward("admin/");
      <%}%>
<%if(request.isUserInRole("others")){%>
        request.forward("usualuser/");
      <%}%>

Deploy your web app. And in browser enter http://your-host:8080/yourwebappPath/protected/firstpage.jsp

And based on your user role you will be redirected to necessary page