If there will be some other ignorant like me, searching for answers be advised you have to set VariationContext on the IVariationContextAccessor.

And you can iterate thru available languages via ILocalizationService.GetAllLanguages()

so than my implementation looks like this

var languages = localizationService.GetAllLanguages();
var items = languages.SelectMany(language =>
{
    _variationContextAccessor.VariationContext = new VariationContext(language.IsoCode);
    return publishedContentQuery.ContentAtRoot();
}).ToArray();