Back-rower Jordan-Roberts, who had been on loan at Hunslet, has signed a contract until the end of next season.
Prop Ormondroyd, who has featured on dual-registration for Featherstone Rovers this year, will spend the rest of the current campaign on loan at York.
Jordan-Roberts, 19, joined Rhinos from Oulton Raiders and made one substitute appearance in each of the 2016 and 2017 seasons, as well as having a spell on loan at Bradford Bulls last year, but has not featured for Leeds this term and his contract was due to expire in the autumn.
Ormondroyd, 26, has made 14 first team appearances for Rhinos - eight of them this year - since signing from Featherstone ahead of the 2017 season.
Rhinos director of rugby Kevin Sinfield said: “This is a great deal for Josh as it allows him to plan ahead for next year when he would be out of contract with ourselves and Jack will benefit from regular game time at York.
“Under James Ford, York are building an impressive club and will be keen to gain promotion this season which makes it a great environment for both Josh and Jack to be part of.”
Ford, the York coach, said: “I am pleased the club has continued to back me by bringing in these two players.
“Both have plenty of quality, appetite for work and potential to play consistently at a very high level.
“I’m looking forward to working with them both and facilitating their development.”