Is it possible to have group vars defined in roles?

For example I have the following structure in my role repo:

my_repo
|-defaults
| |-main.yml
| |-debian.yml
| |-redhat.yml

In debian.yml I have defined a variable called ssh-package as well in redhat.yml but with different values.

If I install my role with ansible-galaxy and I have hosts defined in group redhat or debian, they wont pickup the variables. Do I need to specify the roles variables inside my target structure?