Schofield, 43, who spent time on Glanford Park's backroom staff last season, had been worked with the Robins since March.
He had been assisting the manager Martin Allen and being paid only expenses, but has been rewarded with a formal deal.
"It's a pleasure to come into work every day, it's a great environment," Schofield told BBC Radio Gloucestershire.
"That's all set by the manager and I love his ideas and forward thinking and that was a big draw."
Schofield managed Lincoln City in the 2006/07 season and has also coached at Walsall.