Fosu-Mensah, 20, and Loftus-Cheek, 21, arrived in south east London last summer, brought in by manager Frank de Boer whose spell in charge at the club lasted just five games. The two youngsters have made a more lasting impression at the Eagles, however, with Loftus-Cheek swiftly nailing down a first-team role, having started 15 of the club's Premier League matches this season and forcing his way into the England picture in the process.
Fosu-Mensah has rose to prominence more recently, turning in a man of the match display as Palace secured a draw against runaway leaders Manchester City and has since made the right-back slot his own.
His impressive performances over the festive period sparked calls from United fans for the club to recall the Dutch talent, during a period where first-choice right-back Antonio Valencia was out of the first-team picture through injury.
But speaking on the Five Year Plan podcast, Parish insisted there was no possibility of either player returning to their parents clubs this month. The Palace co-chairman added: "And I don't think the clubs would want that [for their players to return early]. I think the clubs sent them to us knowing it's a two way street, we get a good player and we develop them.
"They should be very happy with what's happened to those players, the game time they've got, the coaching they have got. It's all very well, playing in training and playing in under-23 games but Roy teaches players how to win football matches in the Premier League which is an invaluable skill."
Fosu-Mensah recently revealed he has been in frequent contact with United boss Jose Mourinho and hopes to return to Old Trafford to win a first-team role next season, but insists his focus this term is on Palace.