Do or Don't
I started learning Italian, than decided to challenge myself and learn Romanian also. Was that a good choice? I want to push myself! But what if one language is my limit?
It is probably too early to start another language, particularly one that is so similar to the one you are learning already. Work on Italian for a little while before tackling another language and when you do, it is better to look at one less closely related, like a Germanic tongue or Welsh. After you finish the Italian tree, then I would consider the Romanian tree.
You'll find out your limit as you go. One language is my personal limit, but many people can handle two, or even three at a time. Try Romanian for a small bit, if it doesn't work, then do Italian. I also recommend trying a less similar language alongside Italian, like a Germanic one.