Thanks for your response and describing what formulas you're currently using. I recommend taking a look at this community post which addresses a very similar question. Because you're displaying these numbers by role in a shape that is separate from your org chart, you'll need to utilize two formulas - one to sum the number of employees by role type using a combination of DOWNSTREEMDEEP and graphnodes (which will allow the calculation to perform correctly even when the org chart is collapsed) and a second to pull those sums into your separate table to display them.
In the linked example the user is summing direct reports but you can replace the custom field in that instance - "Direct Report Count" - with yours that contains the employee role. Please let me know if you have any additional questions and refer to our Formulas documentation for any specific formula references.