Did a forum search for 'process credit cards role' (without quotes) and I can't tell what this role does. If I don't check this for users, like anonymous or registered,, does not checking the box mean they can';t order using a credit card?. What about the 'orders' roles? Which ones, if any should I check. I can't really tell what these roles allow.
Generally, in the case of permissions, always avoid granting them whenever possible. You can always add permissions as you need to, once you sort out which ones you need.
Specifically, the process credit card permission is created by ubercart so that you can create an 'order processor' role, and give that employee the ability to process credit cards, without giving them other admin privileges. Generally, you should not check this box for anonymous, or authenticated users. They will still be able to pay with a credit card. Someone on the admin end (either a unique role, or just a general admin) will want to actually process their card, so they should be the ones to have that permission.
As for orders roles, you probably want authenticated users to be able to see their own order, but that's about it.
Without knowing more about your use case, I can't guess what permissions you need for which user. For instance, uc_marketplace, and uc_node_checkout would alter the standard permissions configuration, which you can explore at demo.ubercart.org . Just follow the login directions, and feel free to take a look at a standard (sort of) permissions set up.