ZMP Center Controller reported a B737-900 reported a temporarily loss of control due to a Wake Vortex encounter from a B777 jet 10 miles ahead descending through their altitude.

Narrative

There were bad rides at and above 32000 ft. and Aircraft X was at 36000 ft. initially and looking for 30000 ft. He was 10 miles ahead of Aircraft Y on the same course. I didn't think to call the wake turbulence to Aircraft Y as the Aircraft X; a heavy Aircraft X; was descending in front of him and through his altitude. Aircraft Y asked me what type of aircraft just descended in front of him and I told him it was a heavy Aircraft X. He then said that would have been nice to know as they got rocked pretty hard from the wake turbulence. I apologized and asked him how bad it was. He said they banked 30 degrees.I recommend training all controllers on the importance of alerting pilots of the potential for wake turbulence when a heavy aircraft is climbing or descending in front of another aircraft. It was something that is complete common sense after the fact but at the time I had never really thought about it. This is the first time I have had an aircraft report wake turbulence and it just didn't occur to me at the time that they would encounter it. This would be good to add into the simulation lab during D-side and R-side training and for refresher training. I feel dumb because it is common sense but I have never seen this event happen in the simulation lab or in real life.