Look at the user doc
Basically, in your WEB-INF\xxxx-object.xml file that define your page, you need to add
in the deployments->deployment->page tag
In practice, there's a number of things that can screw you up:
1) you need to change your if-exists definition to overwrite from keep in your deployment->deployment application
2) Your new role may not be defined properly (I don't remember correctly, but it has something to do with the role name shown in your portal admin page should not be the one you use in your xxx-object.xml file) I would suggest using Admin(the built in one) as a role to test first.
Hope this help.