My experience is pretty consistent with that of the Principal Engineer candidate who gave a review here on Mar 2, 2016. I was initially approached by a recruiter about a software engineering position. The recruiter did the bare minimum of arranging a phone screen, and did not follow up with a description of the position(s) I'd asked for. The phone screen was a high-level employment experience discussion with a hiring manager, which went fine. This was followed by a code test, which I took, and then by.... silence. No followup from Roblox or their recruiter, not even a "thanks for taking time to take our test." This lack of basic professional courtesy simply doesn't bode well, so I decided not to follow up on my own.
Now, a few words about the code test. To be frank, the test environment is substandard. If you're familiar with HackerRank or CodeFights, TestDome is what I imagine those products may have looked like in early alpha. In fairness to Roblox, the invitation email did say "C++ Test", but that was the only warning I got that it may be language specific. TestDome does not let you work in your language of choice, and both questions required working knowledge of C++ std library or STL classes to implement elegantly. I was not provided with any hints about what to expect (bear in mind, they knew they were sending this to a Java programmer).
Both code tests had 1-hour time limits. The first test was a type of search, and was suited to a data structure I work with regularly in other languages, so I was able to complete it in well under the allotted time. The second test required fluency in manipulating strings in C++, which I do not have (and didn't, even when I worked in C++ years ago). This is a strange type of problem to screen for a game engine/rendering position. I spent the majority of the hour reading std library documentation and didn't really have time to work out a proper solution to the problem before having to throw down some last minute code. The large countdown timer going in the corner of the screen didn't help things any.
Unlike the other code test sites I mentioned, TestDome does not show you the input or output of the unit tests, only the pass/fail counts. This is not a useful feedback loop. The tests really couldn't be any less like a real world coding situation. Feedback about the unit test outcomes would have been particularly helpful on the second question, as the requirements were incompletely defined; what I wrote passed the example cases in the question, but failed "hidden tests" :-/
I would advise Roblox to come up with a more appropriate screening process, and to follow up with candidates that take time to do their tests or interviews. They are very likely passing over good, qualified candidates with their combination of testing process and lack of communication.
