How to add custom headers to httpd via script?

I am trying to add custom headers to apche httpd 2.4.6 dynamically. Currently, I am using a separate vhost file that has a long list of If ElseIf directives that assign values based on another header in the request.

RequestHeader set "X-Forwarded-User" %{X-Forwarded-User}s

<If "%{HTTP:X-Forwarded-User} == 'user1'">
  RequestHeader set "X-Forwarded-Roles" "role1,role2"
</If>
<ElseIf> "%{HTTP:X-Forwarded-User} == 'user2'">
  RequestHeader set "X-Forwarded-Roles" "role2,role7"
</ElseIf>

Currently the values are hardcoded in the file. I would like to use some sort of script that will get the values from an external source, such as a database.

I get the User header from an external identity provider, but that source cannot provide me with the roles I need.