Roles and permissions are 2 different things but are related. Roles have no intrinsic permissions but places where there are permissions that can be set allow you to choose which roles can do the thing. Pages (Page Settings) have view roles and edit roles as do feature instances, and other permissions are also available under Administration > Site Settings > Security > Permissions where you can specify which roles are allowed the permissions available there. And in custom features it is possible to create/define whatever additional permissions related to your feature you want to enforce but it is also up to you to enforce them within the feature code by checking the user's roles against the allowed roles.

Hope it helps,

Joe