how to roll Tomcat 5.5 / 6 main logs

Question

hi im using tomcat as servlet container for my web app , now im controlling my web app logs with log4j and its has its own log4j jar and its own log4j configuration file
but now i need to control the main tomcat logs (Catalina.out for example) .
i need to roll then by size and control its debug level how can i do that
without adding log4j to tomcat and to use the build in tomcat logs