Send personalized email to a particular role
Try using the views_send module instead. This powerful module acts like views_bulk_operations in that it lets you create a view to execute an action using Drupal's batch API for processing. For your case (roughly following the directions on the project page):


Create a view of users and add the user email field to the list
Add the field 'Global: Send e-mail' to activate the Views Send functionality
Add any other fields that you want to include in your customized email as fields in the view (ex. User: First Name, User: Last Name)
Finally, add a filter to filter by the particular role(s) you want to filter on.
You probably also want to secure the views permissions so non-authorized users can't use the view to send to your users.


If that's all setup then when you visit your page, you will see a list of all users in that role with the option to send an email to them. When you select your users and are ready to send your email, you will then see on the next page the option to use any of the fields you've selected above as tokens in your email (thus the customizable option):