In order for your customRole to see the Pages tab , you have to go to Administration >> Backend Pages and set there the permissions accordingly. From then on I'll try to give you some pieces of advice how to achieve the desired functionality.
1. Create/modify/delete pages within a certain branch - in general you can set create/modify/delete permissions for the whole Pages section. You can give your role View permissions to Pages, and then set additional permissions only to the desired branch (from Pages >> Actions >>Permissions of the Parent page).
2. Create news stories and modify/delete only stories create by someone in their role - that is a tough one, unfortunately such permission rule is not implemented, what I could advise you is to give your customRole permissions to create news, and then maybe individually set the permissions to the news items this role can edit, as a workaround, because giving your customRole modify/delete permissions will be global for all news stories.
I hope this helps you achieve the desired functionality, if you need any further assistance, please do not hesitate to contact me.
the Telerik team