I applied through a recruiter. The process took 3 weeks. I interviewed at Roblox (San Mateo, CA) in Aug 2015
Interview
The interview process began with two hour long phone conversations that lead to an on-site interview. The on-site consisted of an introductory lunch, then one-on-one interviews with five key members of the company.
I was extremely impressed with Roblox. All the interviewers were professional and very sharp. The interview difficulty seems well calibrated. I felt like I was asked questions which were adequate to assess my competence, without lapsing into the kind of pointless obsessions with very narrow, specific knowledge that you sometimes see in these kinds of interviews.
Overall, I had a very positive experience, think they are very smart people doing very interesting work and would have liked to have been ale to accept their offer; ultimately, this position didn't make sense for me given my current position and the cost of living in the Bay Area, but I was very impressed with these folks and highly recommend Roblox overall.
Note: I've listed the interview process as 21 days, but that time-frame was really my fault. I was unable to schedule immediate travel and the Roblox team was completely understanding of this.
Interview questions [1]
Question 1
Q: How would you architect a service that would detect and protect nodes that were being attacked by bots?