"This is a great opportunity," Joyce told the club's website.
"And if I can manage to do half as well as Sean, then we might meet up again in January with both of us eager to lead the line."
He added: "I am very excited at the chance being offered to me".
Joyce goes straight into the Rovers squad for Saturday's home game against Stevenage Borough.
Meanwhile, Forest Green have announced that the registration of defender Josh Ford has been cancelled and Marcus Palmer has been allowed to sign non-contract forms for Evesham United.