Mitchill, a former United Technologies executive, replaced Toby O'Brien, who stepped down after six years as finance chief.
Panos Kakoullis will join Rolls as it tries to weather the historic aerospace downturn resulting from the coronavirus pandemic.
The company is battling reduced demand amid the COVID-19 pandemic, with commercial aircraft sales down 56% in Q3.
Most of the cuts will come in the civil aerospace division, which makes engines for Boeing and Airbus.
The company shipped a record 202 commercial aircraft in Q3 but its KC-46 military tanker program continues to experience delays.
The company's aerospace unit will remain in its portfolio despite pressure from activist investors to spin it off.
The $7.8 billion deal gives the defense contractor access to the small satellite market and boosts its presence in the missile business.
Like other aerospace suppliers, United Technologies is seeking to cut costs and enhance negotiating power in the face of pricing pressure from customers.
The company ended a tough 2016 on a high note as its focus on lowering costs delivered profits that topped analysts' estimates.
A finding that a Washington state measure amounted to an illegal subsidy given the EU a partial victory in a trade battle with the U.S.
"It’s really the transition to the digital airplane that's creating the perfect timing to bring these two entities together," Rockwell says.
The aerospace giant is taking longer to pay its supplier bills after depleting its cash pile to buy back shares.
