There is no fake checkout process, you must enable commerce to test it or you can test it on demo.mojoportal.com or storedemo.mojoportal.com
It is possible for users to checkout without registering or signing in if the product is of fulfillmenttype none, if the cart has any download products then the user is required to sign in or register. So for example people can buy me a beer without registering if they want to. If the order comes back and matches an existing user email address the order will be attached to that user account or if not a user is automatically created using the email address that comes back with the order from PayPal or Google.
There is nothing to enable products by role within a store, but you could create a private store on a page secured by view roles so that only members of the role can browse or purchase items from that store. You could have a different store instance for other users who are not in the role.
The WebStore should be considered an alpha feature at this point. It can be used and I am using it as are some others but its not a finished feature, there is a lot left to do before I will consider it really ready for general ecommerce scenarios.
Hope it helps,