Hey friend! Easier said than done, but try not to be anxious.
Some schools may only give out notifications on a certain date -- one of the schools where I interviewed last year told everyone we would find out in March, even when we interviewed in October. It was a long wait!! Other times, they'll let a few folks know early and then waitlist many others.
Even if the school you mentioned said they are "rolling," they may mean the latter as I described above, in that some applicants will know quickly and others (or oftentimes most) will be put on some version of a waitlist. As it looks like another SDN'er has mentioned, don't freak out if you are still waiting!!! Remember that many of those who get the early offers will end up getting many, many offers and might not end up at your school of interest in the end. It's a long, long cycle, but know that even if you're waiting until April 30 (my situation this past year), it can still work out for the best!
Did you follow-up with the program after your interview to express your interest? If not, this could be an appropriate time to do that. I would not suggest just emailing to ask when decisions will be handed out... although I doubt this is something that could actually hurt your admission, I suggest being craftier about it!
If you have not already contacted them, one idea is to send an "update of interest." This was something I used a lot last year to both reaffirm my interest in a school, show how I might fit in, and let them know what I was doing in my senior year of college. A typical letter of this format might express that you really enjoyed your interview experience, give them a specific researcher who you spoke with whose lab you'd love to learn more about because it's a great fit for you, and have maybe a sentence on any kind of update that you have (an award you've won since the interview, a talk you've given, etc).
The trick is to do the above in as few words possible (not like my posts ugh sorry lol I'm a chatterbox) so that programs don't have to read too much.
The school may respond letting you know more information about where you stand. But if they do not readily provide you an update, I personally found that it was better not to ask. They likely do not know exactly when you personally would hear. With an update of interest, you have given them the chance to share information, but also opened the door for you to reaffirm your interest again later down the road and at that time ask for any updates on your status. A month is still pretty early out, but it's almost always a good idea to stick your foot in the door and show some interest if you haven't yet! That is, of course, just my personal suggestion and another option for you to consider.
Let me know if you have any questions, and good luck to all!!