Yep! The oldest reconstituted root is Old Persian "vrinǰi" . That gave rise to Persian "گرنج", Arabic "رُزّ", and Ancient Greek "ὄρυζᾰ". That Ancient Greek word in turn gave Hebrew "אורז", Arabic "أَرُزّ" (yep, those are two separate borrowings), and Latin "oryza" (later "risus"). The Latin word is the root of most Western European words for rice: English "rice", German "Reis", Italian "riso", French "riz". But the Portuguese/Spanish/Ladino "arroz" actually came via Arabic "أَرُزّ".
In both words - אוכלת and אורז - the vav alone represents the O vowel. In different words the vav can represent the U vowel, such as in אולי ("ulai" maybe/perhaps) and אולם ("ulam" a hall such as a dance hall or a wedding hall). So the alef does not determine the sound of the vowel represented by the vav.
The vav is an interesting letter with multiple uses, adding complexity to the language and challenges to our studies.
it's pronounced like oh-rez. http://forvo.com/word/%D7%90%D7%95%D7%A8%D7%96/#he
For Duo, I use the Duolibro extension for chrome https://chrome.google.com/webstore/detail/duolibro/ogianofickehjjgaopiohbgjhmhbdafn