1) I know a few kids that went on to great schools that were addicted to various video games. In general, all of them are successful today, a couple decades later. In only two instances, did a parent actually have to intervene. One sent their kid to a sort of "boot camp" and the other grounded the kid for a year. Both of these were in high school.

2) Which game is it? Roblox is generally geared towards children - it's not exactly a mature game or audience. The gaming sounds like less of an issue than the choice of game. I would actually try to find out more about the game and what interests them about it.

My personal opinion is: hands off, supportive, but make your thoughts known - they are their own person and not every mistake leads to a life of disaster. If they got into a great school, they will land on their feet one way or another. But 19 is pretty old to have a video game issue, so it might be a symptom of other problems.