{   package Child::Creator;
    use Moose::Role;
    requires 'child_context';

    sub create_child {
        'Child'->new(context => shift->child_context);
    }
}

{   package Parent;
    use Moose;
    with 'Child::Creator';
    sub child_context { 'parent' };

    __PACKAGE__->meta->make_immutable;
}

...