"Rosa and Judy"
in Semitic languages «and» is a syllable added to the beginning of the second word. «wa-» in Arabic («ve-» in Hebrew).
The pronunciation can be modified sometimes depending on the beginning of the word, so it can even be «u-» but it's spelt with the same characted «وَ»
The word should be written without breaks but there should be space after the first word like «Rosa andJudy»
Not in all Arab countries. There are actually 2 competing standards for this. We, in Lebanon, put a space between وَ and the word after it, and I think it would be better for the course makers to adopt that standard in this case, because it's a lot easier for beginners to learn, and it makes adding hints and tips under words a lot easier too, because people can hover (or click) on وَ separately.
In a different translating exercise the question was raised why the name Rosa translates or is pronounced as something like Rusen, why the n at the end? The previous answer had to do with the end of a sentence but that is not the case in this exercise.. Thanks for any clarification!
You know to say «o» because you know a name Rosa, but there is no word Rusa. If you don't recognize the word, tough, you will not know how to pronounce it. This is a problem with Semitic languages you have to get used to. Some letters stand for more than one sound, and some vowels are not written at all.
Native speakers know how to read it because they already know the language, so they recognize most of the words. If there is some very rare word, they have a chance to guess it based on some patterns and context, but a learner like us has to find a dictionary with pronunciation or ask a native.
English also has this problem - why do you say «blad» («blood»), «flor» («floor») , and «mun» («moon») - what is the real pronunciation of «oo»?
The thing is English language is most exceptional one, and is not a great example. German and French has rules and they stick to it, Ukrainian and Russian has rules and they stick to it as well. From what i can see Arabic is quiet strict language. And if they have an exceptions i would like to know it.
The greatest example that shows oposite side you didn't mentioned in your statement is japanese. It apears that this language is strictly syllable and their amount is less than you can build in most other languages, so they replace them with the closest one by sound of existing japanese ones. So they would read (if not translating, cuse names mostly won't) "Lily" as "Riri", "Olivia" as "Oribia", "James" as "Jemuzu", "Charles" as "Charuzu", etc.
So the question still relevant "would Rosa writen in arabic روزا readed as Rusa", question not about is it an actual word, but would it be readed that way by native Arabic speakers. Because i don't see any "o" later, or mentioning about reading "و" as "o" in certain cases.
Classical and Modern Standard only have three vowels, (i, a, u), each of them can be short or long, so six in total. Short vowels are usually not written, but can be indicated by diacritics. Long vowels are written with letters than can also stand for consonants. In Standard Arabic words the letter و (waw) can be a consonant w or a long u.
If this was an Arabic word it could be pronounced rusa, but it isn't. Without full vocalization you don't know how the word sounds. It could just as well be rawsa, riwsa, ruseh, etc. In a good dictionary this should be made clear by diacritics. D y knw hw t prnnc ths wtht dctnr?
As to what woud a native speaker guess the word to be without diacritics, lets wait for other comments. The problem with native speakers is that most of them speak dialects, not the Standard. And most of them will tell you their dialect is the best and all the others are broken. In modern dialects of Arabic many sounds are different. For example in Egyptian, i may be pronounced e, and u may be pronounced o. Egyptian TV is very popular in many Arabic countries.
TL,DR. In standard Arabic the letter waw stands for w or u. In some Arabic dialects the letter also means o in some words. When you write English words or names in Arabic w, o and u are written with the same letter waw (و).