I want to mass include .yml files under the tasks folder when a condition is met, something like
- include:
- foo.yml
- bar.yml
when: ansible_os_family == “Debian”
Is it possible currently?
no, includes are not conditional.
what that does is add the condition to each task in the includes.
So it’s basically the same thing in the end 
Note that this behavior is improved in 1.3, where if you have any conditions they are inserted before any conditions in the task.
I also highly recommend the group_by module for conditional application of roles.