I think it would be great to have at least two predefined roles that are built into ubercart.
One for a shipping manager. This would be so when they log in, all they get to see is the ORDERS pages, and have rights to view orders, change their status, and enact workflow related to moving orders through the shipping process.
This role would restrict this person so they cannot mess up anything else with how the cart or site is structured.
The Product Manager role would only allow this person to create a new product, or update the fields in an existing product, with no access to other nodes or to the other cart config options.
I tried to create these myself, but did not achieve the level of restrictiveness I was hoping for, so I think adding it to base would be cool.