The 46-year-old was charge for two years at the Priestfield Stadium and has also previously been assistant-manager at Burnley alongside Stan Ternent.
Palace boss Neil Warnock told the South London Press: "We are delighted to have Ronnie Jepson on board. He has great experience, especially working with the forwards.
"It's a good opportunity for him as well. He has promised me he will stay for at least a season - even if another manager's job comes up."
The Eagles have not had anyone in charge of their second string since Kit Symons left the club in October 2007.