It took me a while to figure out that I actually had to stop the timer as well, I thought originally it was some sort of roulette, but then realized shortly afterwards that I also had to stop the timer. Simple, but effective gameplay, using the countdown of the timer as part of the mechanic. I don't I'd particularly consider the rage timer to be a count down (rather a count up), maybe if it was labeled User Patience and decreased instead?
I think my main feedback would be either slower dice rolls overall (I never touched the button at the beginning because the combination of high timer plus whatever the dice gave would ALWAYS be too high sometimes, but if we could fine tune it and choose a number a bit more effectively) OR have the dice roll actually be counting down rather than random so I know if I manage to catch a flash of a 6 as it flails away in there, then if I'm quick enough I might catch a 5 or 4.