How long will it take to have a good command in Romanian if I speak other Romance languages ?
How long will it take to have a good command in Romanian if I speak other Romance languages like French ( fluently ) and others ( intermediate skills ) ?
As far as I see the vocabulary can get too different from the once in most of other Romance languages.
So, how complicated the Romanian language actually is for those who speak other Romance languages ?
Chances are, you'll hear a lot of vocabulary words in Romanian and say "oh yeah! I know what that means!"
If you're really dedicated, you'll pick up Romanian pretty fast, but you have to put a lot of effort into it.
What I'm saying is that (in a way) you would have to dedicate your life to learning Romanian, and not just a side hobby.
You specified French, and what I've noticed amongst Latins learning other Latin languages is the following: For some speakers it will be easier to learn a specific Latin language than vice versa.
Speakers of Romanian might say that it is really easy for them to learn Spanish, while Spanish speakers might say that Romanian is not that easy to learn, and although a lot of vocabulary is in common, learning the grammar is way harder (things such as the definite article placement, cases, etc.)
In short, it really depends on your level of dedication.
Dedication in multiple Latin languages
As you can see, it would be most easy for a speaker of latin to clearly understand this word in Romanian, in second place would be a French speaker, and then everyone else. Just thought I'd give an example that matches the answer to the question. ;P
It depends on you and how much time you spend speaking and listening to the language. Also with which techniques you acquire new chunks and make them usable in conversation which is an individual process that happens while practicing to speak. If you don't speak a lot you will not suddenly be fluent.
I don't mean listening to the separate sentences and words on Duolingo. There is nothing bad about them but I mean speeches, dialogues, talk shows, news, radio, audio books, short stories and other materials.