I am using ubercart and Roles module to sell some roles on my drupal 7 site. I wonder whether I can sell multiple roles with a single product, I tried to add multiple roles to a single product under features, but after purchasing a product I found only one role is assigned to the purchaser, Is there any way I can assign multiple roles.
Yes, the UC Roles module can assign multiple roles on purchase. All you need to do is add each role assignment you want at /node/XXX/edit/features.
If the roles aren't being assigned after purchase, you might want to check the SKU options you have for each feature. It could be that your product purchase is a SKU that isn't configured for role assignment. If that isn't it, you should check to make sure that your checkout rules are configured to set the right order status to trigger role assignment.