So this is a real quick and easy way to restrict all orders from a websites or store views in your magento for a selected user role.
find this file in your magento install: /app/code/core/Mage/Adminhtml/Block/Sales/Order/Grid.php
i do recommend you copy and edit a version of this file over to your local code folder.
now around line 59 find this line
$collection = Mage::getResourceModel($this->_getCollectionClass());
and below add this code
$admin_user_session = Mage::getSingleton('admin/session');
$adminuserId = $admin_user_session->getUser()->getUserId();
$role_data = Mage::getModel('admin/user')->load($adminuserId)->getRole()->getData();
$role_name = $role_data['role_name'];
change these parts to your requirments:
USER_ROLE_HERE = the role name of your user permissions role ( in magento: System > Permissions > Roles )
STORE_ID_HERE = The Store ID of the store view you want them to only have access to. you can get this by going to in magento: System > Manage Stores > click on your store view name and then look in the browser url for something like /store_id/9/ where the number = your store id.
if you want to change it to a website and not just a store simply change the filter from store_id to website_id and get your website ID via the same method above but instead of clicking on your store view name, click on your website name