Creating database static data (roles, adminstators accounts)

Hello! I have a task to create some static data in database (for
instance, bunch of user roles or administrator account).

Certainly, we should not create it up in our migrations.

If we create them in initializers, we'll have to check if data is
already in DB and even if such table exists (otherwise, rake tasks,
even db:migrate will fail).

So, is there some brilliant solution?

How about using a custom rake task?

I'm curious though, why can't you create them via a migration?