Recommendation for modules/workflow to build a premium link directory
I'm building a site with free and paid memberships now; my use case isn't exactly the same but I'll share what I can.

I'm not using Drupal Commerce; in my case, users make a payment with PayPal and then I manually add a paid role to each account.  I intend to eventually set this up in Drupal Commerce but I haven't had the time yet.

When I add the paid role, a rule is triggered that automatically sets an expiration date using the Role Expire module.  Until very recently the 7.x rules integration was bugged but I am happy to report that it is now fixed and works great.

As for working with Commerce, Randy Fay also did a screencast on setting up content access for a membership site.  I'm not sure if the content access part is relevant but the final part of the screencast covers:


  
  Create a product representing the premium role.
  Create a rule that grants the premium role on order completion:
  
  After updating an order
  If the order state is Completed
  And the order contains our premium product
  Add a role to the user who is the owner of the order