I would be extremely wary. It's true that the ingredients list on paper appears pretty solid, but who knows whether that's actually what goes in there. Read the reviews on the Slovenian site, they're completely fake and randomly computer-generated, not actual reviews by people who have bought and tried the food. And I wonder if the food is truly produced in England; Roni appears to be a brand of Sam Mills, a Romanian company (unless we're talking about two Roni's here).
https://www.behance.net/gallery/19937791/Roni-Pet-Food
https://en.wikipedia.org/wiki/Sam_Mills_(company)
Sam Mills is a supplier of pasta and other grain products to WalMart, a chain known for selling cheap and poor quality products:
http://www.walmart.com/c/theme/sam-mills-sam-mills-collection
I looked into this food after reading this post:
http://www.pesjanar.si/forum/index.php?action=profile;area=showposts;u=12045
I was unable to identify the name of the Slovenian distributor, this tanjajang, who recommended the food here, is probably someone with a commercial interest in marketing the brand in Slovenia.
If it can be independently verified that the ingredients are as listed and the food is produced in the factories claimed, then it might indeed be worth a try. I was all set to try it myself, but I was put off by the fake reviews and the possible Romanian connection. Sam Mills is a major manufacturer of grain products: it strikes me as extremely odd that they would get into the business of producing high quality, grain-free pet food.