Gulfstream IV First Officer reported an inflight upset resulted after encountering wake turbulence from a preceding Boeing aircraft inbound to PHX in descent through FL250.

Narrative

We were flying along at FL410 and given a descent clearance to cross Scole at FL250 Maintain 300 its or greater in transition. I advised we were unable altitude but will give best rate as descent clearance was given late. We were descending 4000ft per minute and vnav was still dropping indicating us needing a greater descent. ATC cleared us to be higher and to give best rate; we were given a frequency change and leveled at Spink with 300kts and changed frequency. At the moment of leveling the autopilot kicked off and plane banked 60plus degrees to the left and right while dropping altitude. Both captain and copilot grab the controls to counteract the roll together and we're fighting it. ATC had leveled us 5nm in trail of what appeared to be a Boeing and we were encountering major wake turbulence. We were having a hard time maintaining wings level and altitude and called ATC letting them know we are offsetting to the right due to wake turbulence as we turned to gain controllability of the aircraft. ATC then instructed a 120 degree heading which was maintained for a while. After being cleared direct geela and given frequency change the controller told us it was an issue offsetting due to restricted airspace and it was our responsibility to fly the plane. I informed him it was major wake turbulence and it was needed for control ability. It's ATC responsibility to maintain a separation distance and not following arrival speed and altitude procedures cause this deviation from our flight course.