Center Controller reported a wake turbulence event between a CE-525 and a heavy B767.

Narrative

I was working Sector X. Aircraft Y was at FL280. Aircraft X checked on out of low; climbing to FL250; requesting FL300. I had traffic at FL300 so I couldn't climb them to the requested altitude; there was traffic diverging behind but much faster at FL280; so initially I climbed them to FL260. When I was comfortable climbing them; I called the traffic to Aircraft X on Aircraft Y. They were 12 miles behind; I gave them a wake turbulence cautionary; and climbed them to FL280. As soon as they leveled; the pilot said they had 'hit massive wake turbulence' and asked for a different altitude. I descended them back to FL260. I asked them if they were OK; they said they were checking. They mentioned that the aircraft had rolled 90 degrees. I also saw that they had strayed slightly off course to the north side of the departure/jet route. I told the Supervisor about it and they said they were fine. There was no damage or injuries. I'm glad I gave them the cautionary; so at least they weren't completely taken by surprise.I really wish we had a way to detect conditions where wake turbulence might be worse or might not dissipate as quickly. Generally I try to get at least 10 miles in these situations involving a heavy at the same altitude; but there was 12 miles increasing and the aircraft still encountered an unsafe condition. I think we need some procedural changes in enroute; including using the word heavy for heavy aircraft; increased separation for disparate weight categories; and more emphasis on these conditions. Additionally; I think we need more training on wake problems in enroute and the conditions that make it more likely to occur. Things like the B738/9 generating a lot of wake turbulence (more than a B752); the A321 problems; the A20N and A21N; and; obviously; the heavies and supers. This should especially include disparate types like turboprops and biz jets where the smaller aircraft is adversely affected. Information about the accuracies of RNAV where they are much more directly behind should also be emphasized.